DEV Community: Srikar Phani Kumar Marti

Debugging Complex Pointer and Touch Event Interactions in Mobile Browsers

Srikar Phani Kumar Marti — Tue, 04 Aug 2026 14:31:01 +0000

Ever tried to build a smooth swipe or pinch gesture on mobile only to find it firing weird events, missing touches, or blocking scroll? If you’ve been there, you know it quickly devolves into a maze of event handlers, mysterious no-ops, and contradictory docs.

I recently spent days debugging a custom gesture recognizer for a mobile web app and finally got to the bottom of how browsers handle pointer, touch, and gesture events differently on mobile versus desktop. Spoiler: it’s not just about firing different events , it’s the event order, default behaviors, and subtle browser quirks that trip you up.

Let’s get practical. I’ll share concrete examples, what’s going on under the hood, and exactly how to debug these interactions using Chrome DevTools.

The moment things got weird: touch events firing but pointer events missing

My app needed to detect a two-finger swipe. I started by listening to pointerdown, pointermove, and pointerup events because pointer events unify mouse, touch, and pen input nicely on desktop.

On laptop browsers, this was smooth sailing. But on mobile, sometimes the pointer events never fired, or fired inconsistently. I was baffled.

Digging deeper, I learned that on mobile browsers, pointer events are often built on top of touch events but with extra layers of logic to handle gestures and scrolling. Sometimes the browser suppresses pointer events after detecting a gesture like scrolling, or delays them until it’s sure the user isn’t zooming. This behavior differs a lot across browsers and platforms.

Here’s a quick example:

el.addEventListener('touchstart', e => console.log('touchstart'));
el.addEventListener('pointerdown', e => console.log('pointerdown'));

On desktop emulation, you’ll see both events fire. But on real mobile Safari, pointerdown might not fire at all if the browser thinks the touch might become a gesture.

Why event sequences differ so much on mobile

The event pipeline on mobile is more complex because the browser must decide whether a touch is:

A tap
A scroll
A zoom (pinch or double tap)
A custom gesture

To do this, browsers delay or cancel pointer events based on heuristics like touch slop (how far a finger moves before the gesture is considered a scroll).

For example, if the user places a finger and starts scrolling, the browser may:

Fire touchstart
Delay or cancel pointerdown
Fire touchmove
Cancel pointer events entirely if scrolling starts

This means your pointer event handlers might never get called if the browser claims the gesture.

The tricky default behaviors and event.preventDefault()

Another common trap is the interaction between the browser’s default touch behaviors (like scrolling and zooming) and your event handlers.

Calling event.preventDefault() on touchstart or touchmove can stop scrolling, but:

On some browsers, touch-action CSS is a better way to declare which gestures your app handles
Using preventDefault() indiscriminately can hurt scroll performance and cause jank

For example, to enable custom horizontal swipe but preserve vertical scroll, setting CSS like this helps:

.swipe-area {
  touch-action: pan-y;
}

This tells the browser: "I want to handle horizontal gestures myself, but let vertical scrolling happen normally." Browsers then won’t cancel pointer events for vertical scrolls.

Common pitfalls with custom gesture recognizers

If you’re building gestures from scratch, here are things I ran into:

Mixing touch and pointer events without clear strategy: Listening to both can cause duplicate events or missed ones if you don’t account for the browser’s gesture detection.
Not using touch-action properly: Without it, browsers may cancel pointer events or delay them, breaking your recognizer.
Ignoring multiple pointers: Mobile touch means multiple fingers at once. Pointer events help here, but on some browsers, pointer events don’t fire or lose track of pointer IDs.
Relying on event.preventDefault() too much: Blocks scrolling and hurts performance.

How I debugged these issues in DevTools

Mobile event debugging is tricky because you need to see event timing and ordering on real devices. Here’s what helped me:

Remote debugging with Chrome DevTools: Connect your Android device via USB and use chrome://inspect to debug mobile Chrome. You can set breakpoints in event handlers and watch event objects.
Logging event sequences: I added console logs for every pointer, touch, and gesture event with timestamps and pointer IDs, so I could see exactly which events fired and in what order.
Using the "Event Listener Breakpoints" feature: In DevTools, under Sources > Event Listener Breakpoints, I enabled breakpoints for touch and pointer events to pause exactly when they fire.
Inspecting CSS touch-action: I repeatedly inspected the element’s computed styles to verify touch-action was set as intended.
Testing on multiple browsers: I tested on Chrome, Firefox, and Safari on iOS because they behave differently. Sometimes a solution works in one but fails in another.

A concrete example: building a horizontal swipe recognizer that doesn’t block vertical scroll

Here’s a minimal setup that worked after much trial and error:

<div id="swipe" style="touch-action: pan-y; width: 100vw; height: 200px; background: #eee;">
  Swipe me horizontally
</div>
<script>
  const el = document.getElementById('swipe');
  let startX = null;
  let startY = null;

  el.addEventListener('pointerdown', e => {
    startX = e.clientX;
    startY = e.clientY;
  });

  el.addEventListener('pointermove', e => {
    if (startX === null) return;
    const dx = e.clientX - startX;
    const dy = e.clientY - startY;

    if (Math.abs(dx) > Math.abs(dy)) {
      // Horizontal swipe detected
      e.preventDefault(); // prevent scrolling horizontally
      console.log('Horizontal swipe', dx);
    }
  });

  el.addEventListener('pointerup', () => {
    startX = null;
    startY = null;
  });
</script>

Key points:

touch-action: pan-y lets vertical scroll happen normally.
We listen only to pointer events for clarity.
e.preventDefault() is called only when a horizontal swipe is actually detected, minimizing interference with scroll.

Wrapping up

Mobile pointer and touch event handling feels like a black box until you see the browser’s hesitation and decision tree in action. Knowing the event sequence differences, the role of touch-action, and how default behaviors affect your handlers can save hours of debugging.

Next time your custom gesture is flaky on mobile, try logging every touch and pointer event with timestamps, check your touch-action CSS, and don’t throw preventDefault() around blindly. Use remote debugging tools to watch the event flow live.

You’ll find the browser is trying to help you , it just wants to make sure scrolling and zooming work smoothly, even while you capture your fancy new gesture.

Happy debugging!

Helpful learning resources

MDN Web Docs
web.dev performance guidance
OpenAI developer resources Originally published at Under The Hood. Get the next deep dive in your inbox: subscribe to Under The Hood.

React Concurrent Rendering: Scheduling, Interruptions, and Debugging Suspense Boundaries

Srikar Phani Kumar Marti — Mon, 03 Aug 2026 12:53:45 +0000

You know that moment when your React Suspense fallback jumps on the screen, then disappears, then reappears, leaving you wondering if you did something wrong? I’ve been there , seeing flickers, multiple loading spinners, or even UI glitches around Suspense felt like chasing ghosts.

Turns out, React’s concurrent rendering scheduler is doing a lot behind the scenes , juggling priorities, pausing work, and restarting it , and Suspense boundaries are right in the middle of this dance. Understanding how React schedules work and handles interruptions can save you hours of frustration.

React’s concurrent rendering scheduler: what’s it really doing?

React’s concurrent mode isn’t just a fancy name; it means React doesn’t blindly render your entire component tree all at once. Instead, it breaks rendering work into chunks and spreads it out over multiple frames. This keeps your app responsive to user input and other high-priority tasks.

Imagine you’re painting a huge mural. Instead of finishing it in one go (blocking everything else), you paint a little, step back, listen if someone calls you, then paint some more. React’s scheduler works similarly:

Units of work: React slices rendering into small units it can pause and resume.
Priorities: Some updates are more urgent , like responding to a click , so they jump ahead.
Interruptions: If something more important comes up, React pauses current work and switches.

This model makes React apps feel snappy even when doing heavy rendering or fetching data.

What happens when Suspense enters the scene?

Suspense boundaries are React’s way to say, “Hey, if this component isn’t ready yet (because it’s waiting on data, code, or something else), show this fallback for now.”

Under the hood, when a component suspends (throws a Promise), React marks that unit of work as "waiting," and the Suspense boundary kicks in to show the fallback UI immediately.

But here’s the catch: React keeps trying to finish rendering the suspended component in the background. When the Promise resolves, React attempts to commit the real UI.

Since this happens with React’s concurrent scheduler, the work can be interrupted or retried multiple times before committing, which explains those flickers or fallback flashes you see.

How React prioritizes and interrupts updates

Let’s say the Suspense boundary is showing a spinner for a data fetch. While the fetch is pending, React is rendering lower-priority work. But if the user types or clicks, React wants to respond immediately:

The scheduler interrupts the current render.
It pauses the Suspense boundary’s work.
It starts a higher-priority render (like updating an input).

Once high-priority work is done, React resumes the Suspense boundary rendering.

This pause-and-resume cycle can happen multiple times, which often causes the fallback to appear and disappear several times rapidly.

Why does Suspense sometimes unexpectedly remount or reset state?

One tricky side effect is that when Suspense boundaries retry rendering, React may discard work in progress and start over. This can cause components inside Suspense to unmount and remount , resetting local state.

For example, if you have a form inside a Suspense boundary, users might lose their input unexpectedly if the boundary retries.

This happens because React’s internal fiber tree abandons the current render and attempts a fresh one when interrupted or when new data arrives.

Debugging Suspense boundaries in production

When Suspense boundaries behave oddly, here’s how to get a clearer picture:

Enable React DevTools Profiler: It shows you when rendering work starts, suspends, and commits.
Use React.unstable_trace or React 18’s tracing APIs: They help track update flows and see interruptions.
Add logging inside your Suspense fallback and wrapped components: Knowing when they mount, unmount, or suspend helps.
Check for state resets: If state inside Suspense resets unexpectedly, consider moving state above the boundary or using useRef to preserve values.

Practical tips to reduce flickers and interruptions

Batch updates: Group multiple setState calls to reduce intermediate renders.
Use useTransition wisely: Mark non-urgent updates as transitions so React can better prioritize.
Split Suspense boundaries thoughtfully: Smaller boundaries isolate suspensions and reduce widespread UI resets.
Avoid putting critical state inside Suspense boundaries that might remount.

When you want to dive deeper into the scheduler

React’s scheduler uses priority lanes internally , like lanes on a highway , to organize and reorder work. High priority lanes are for urgent tasks like user input, while low priority lanes are for background data loading.

If you’re curious, the React source code and some community tools expose these internals so you can peek under the hood.

Understanding this helps explain why some updates interrupt others and how React keeps your app responsive even during heavy lifting.

React’s concurrent rendering isn’t magic, but it’s subtle. That flickering spinner or disappearing UI isn’t a bug , it’s React doing its best to balance responsiveness and completeness.

With this inside view of scheduling, interruptions, and Suspense boundaries, you can debug smarter, design boundaries better, and build smoother experiences for your users.

Helpful learning resources

MDN Web Docs
web.dev performance guidance
React documentation Originally published at Under The Hood. Get the next deep dive in your inbox: subscribe to Under The Hood.

How Browsers Handle Keyboard Events: From Raw Input to DOM Events

Srikar Phani Kumar Marti — Fri, 31 Jul 2026 12:57:23 +0000

Ever been bitten by a keyboard event bug where your app gets multiple keydown events for a single press, or where input composition (hello, IMEs!) breaks your form? Or maybe you’ve seen different browsers fire keyboard events in different orders and wondered what’s going on.

I recently spent a frustrating afternoon debugging exactly that kind of issue. The app had subtle bugs: repeated characters flooding inputs, missed keyup events, and weird behavior when users typed accented characters on macOS vs Windows.

Turns out, keyboard event handling in browsers is a surprisingly intricate dance. It’s not just “key pressed, event fired.” There’s a whole pipeline from the raw OS input, through composition and key repeat, to DOM events that your JavaScript sees.

Let me walk you through the journey of a single keystroke, from the raw hardware signal all the way to the DOM event listeners that your code hooks into, and why understanding this can save you hours of debugging.

When you press a key, the OS speaks first

Your keyboard doesn’t talk directly to the browser. It communicates with the operating system, which interprets raw scan codes and decides what key was pressed, taking into account keyboard layout, modifiers, accessibility settings, and input method editors (IMEs).

The OS then sends processed key events to the browser. This is why your keyboard layout or system language can change the keys you get in JavaScript.

The browser’s input pipeline: raw event to DOM event

Browsers receive low-level key signals from the OS and transform them into the DOM keyboard events you use: keydown, keypress (deprecated but still around), and keyup.

Here’s the usual event flow for a single physical key press:

keydown: Fired immediately when the key is physically pressed down.
keypress: Fired only for keys that produce a character value. This event is deprecated but still emitted in many browsers.
input: For text input fields, when the key produces a character, the input event fires to reflect text changes.
keyup: Fired when the key is released.

But it’s not always this simple.

Key repeat

Holding down a key triggers multiple keydown and keypress events due to key repeat. The browser fires these events repeatedly until you release the key, and then a single keyup is fired.

This often surprises developers who expect only one keydown per press. Handling key repeat requires explicit logic if you want to ignore repeats or treat them differently.

You can check event.repeat to distinguish repeated keydown events.

Composition events for IMEs

Input Method Editors introduce another layer. For complex input like Japanese, Chinese, or accented characters, a single character can require multiple keystrokes before it’s finalized.

During composition, browsers emit compositionstart, multiple compositionupdate, and finally compositionend events. The DOM does not emit normal keydown/keypress events for every raw key during composition, or the text input changes might be incomplete or wrong.

Handling composition properly is critical for internationalized apps, or you’ll break input for a large user base.

Order matters: event sequence and quirks across browsers

The exact event sequence can differ between browsers or platforms. For example:

Some browsers fire keypress after keydown, others fire it before.
macOS Safari historically fires keydown only once per physical press, not repeating with key hold.
Windows Chrome and Firefox repeat keydown and keypress during key hold.
During IME composition, key events may be suppressed or delayed.

These differences make debugging keyboard input across browsers a headache.

Practical debugging tips

If you’re confused why your key handler behaves differently across browsers, try this:

window.addEventListener('keydown', e => console.log('keydown', e.key, e.code, 'repeat:', e.repeat));
window.addEventListener('keypress', e => console.log('keypress', e.key, e.code));
window.addEventListener('keyup', e => console.log('keyup', e.key, e.code));
window.addEventListener('compositionstart', e => console.log('compositionstart'));
window.addEventListener('compositionupdate', e => console.log('compositionupdate'));
window.addEventListener('compositionend', e => console.log('compositionend'));

Test typing normal keys, holding keys down, and using IMEs. Notice the event order, which events fire, and whether repeat is true.

Why your input bugs might be composition bugs

If you see your input event handlers getting unexpected partial text or spamming multiple events during accented character input, check your composition event handling.

Ignoring composition events can make your app behave like it’s broken when users type non-ASCII characters.

A common pattern is to ignore key events during composition:

let isComposing = false;

input.addEventListener('compositionstart', () => { isComposing = true; });
input.addEventListener('compositionend', () => { isComposing = false; });

input.addEventListener('keydown', e => {
  if (isComposing) return; // ignore during composition
  // handle keydown normally
});

Wrapping up

Keyboard input is deceptively complex. The OS, the browser, and your app all play a part in deciding how key events flow.

Understanding the event sequence, key repeat, and composition events helps you write more robust input handlers, avoid cross-browser bugs, and build better user experiences, especially for international users.

Next time you debug a keyboard event mystery, remember: it’s not just your code. It’s a whole pipeline under the hood.

Helpful learning resources

W3C WAI accessibility guidance
W3Schools accessibility tutorials
MDN Web Docs Originally published at Under The Hood. Get the next deep dive in your inbox: subscribe to Under The Hood.

Screen Reader Handling of ARIA Live Regions: Timing, Interruptions, and Debugging

Srikar Phani Kumar Marti — Tue, 28 Jul 2026 11:16:13 +0000

Ever had a situation where you update a live notification region in your SPA, but the screen reader stays silent? Or worse, it reads some old message, then skips your update altogether?

I ran into this exact problem recently while working on an accessibility feature that used ARIA live regions to announce dynamic content changes. The updates were there, the DOM was correct, but screen readers just wouldn’t read the new content reliably.

Turns out, live region announcements are not as straightforward as just toggling aria-live. There’s a subtle timing dance behind the scenes, and interruptions can silently swallow your messages. Let me walk you through what I learned debugging this, how screen readers handle live region updates, why timing matters, and practical ways to get your ARIA live announcements working consistently.

The weird silence: live region updates don’t always get announced

I had a <div aria-live="polite"> that I updated with new status messages from an async process. When I tested with NVDA and VoiceOver, the first message would be read, but subsequent updates were sometimes ignored.

At first, I thought my updates weren’t reaching the DOM or the live region was stale. But inspecting with accessibility tools confirmed everything was in place.

Why the silence?

How screen readers process ARIA live regions

Screen readers maintain an internal accessibility tree representing the current UI state. When the DOM changes inside an ARIA live region, the screen reader detects those changes and queues announcements.

But this queue is subject to:

Timing thresholds: screen readers batch rapid-fire changes to avoid reading an avalanche of messages.
Interruptions: a user’s current announcement can block or cancel queued messages.
Change heuristics: not all changes trigger announcements, e.g., if the content didn't actually change textually.

For example, NVDA waits a little after an update before announcing, to gather potential additional changes. If you update the live region content multiple times quickly, only the last change might get read.

The problem with rapid updates and DOM mutations

Imagine your async process emits several updates in under a second. You might:

liveRegion.textContent = 'Step 1 completed';
liveRegion.textContent = 'Step 2 completed';
liveRegion.textContent = 'All done!';

Only "All done!" might get announced, because the screen reader batches the changes and only reads the final state.

Sometimes, if the updates happen too fast, the screen reader might not even detect intermediate changes.

Interruptions: how user focus and speech affect announcements

Screen readers can interrupt or suppress live region announcements if the user is already listening to something else:

If the user is navigating the page with the keyboard or mouse.
If another alert or live region is currently being read.
If the screen reader is busy announcing system messages.

This means your live region updates can be silently dropped or delayed.

Debugging live region announcements

To figure out what’s going on, I tried:

Logging live region content changes to confirm updates happened.
Slowing down updates with setTimeout to space out announcements.
Using different aria-live values like assertive and polite to test priority impacts.
Testing with multiple screen readers (NVDA, JAWS, VoiceOver) since each has quirks.
Using browser extensions like Accessibility Insights or VoiceOver Utility to inspect the live region's accessibility tree.

One useful trick was creating a small demo page where I manually controlled live region updates via buttons and timers. This let me isolate timing and interruption behaviors.

Under the hood: what you can do to improve live region reliability

Throttle or debounce your updates. Avoid flooding the live region with rapid changes. Group related updates and announce consolidated messages.
Clear the live region before updating. Setting textContent = '' briefly before inserting new text can force screen readers to recognize a fresh change.
Use a hidden off-screen live region element. Sometimes toggling visibility or using a separate hidden live region helps isolate announcements.
Experiment with aria-atomic. Setting aria-atomic="true" tells screen readers to read the entire live region content on change, which helps when partial updates confuse them.
Match your live region role to the context. Use role="alert" for urgent messages (immediate announcements) and aria-live="polite" for less disruptive updates.
Test with real users and multiple screen readers. Each has different heuristics and timing rules.

A concrete example: reliable live region updates in a SPA

Here’s a snippet I ended up using for a status message live region:

const liveRegion = document.getElementById('statusLiveRegion');

function announceStatus(message) {
  // Clear the region to reset announcer
  liveRegion.textContent = '';

  // Add a small delay before updating content
  setTimeout(() => {
    liveRegion.textContent = message;
  }, 100);
}

This brief delay and clearing step forces screen readers to catch the change as new content, not just an update.

On the HTML side:

<div
  id="statusLiveRegion"
  aria-live="polite"
  aria-atomic="true"
  style="position:absolute; width:1px; height:1px; overflow:hidden; clip:rect(1px, 1px, 1px, 1px);"
></div>

This setup worked consistently across NVDA, JAWS, and VoiceOver during my testing.

Why this still isn’t perfect

Screen reader implementations vary wildly. Some might ignore live region updates if the user has disabled announcements or if the browser accessibility API behaves differently.

Also, complex content inside live regions (HTML markup, images, or dynamic widgets) can confuse announcements.

The best you can do is:

Keep live region content simple and textual.
Minimize rapid updates.
Test on your target platforms.

What I wish I knew sooner

I wasted hours chasing bugs where live region content was correct but announcements silent. Understanding the importance of timing and interruptions was a game changer.

Also, don’t assume aria-live is magic. It’s a hint to screen readers, which have their own rules and priorities.

Next time you build dynamic live notifications in your app, remember it’s a conversation between your DOM and the screen reader’s internal queue. Getting the timing and content right is how you make that conversation audible.

Give these tips a try and save yourself the frustration of silent live regions!

Helpful learning resources

W3C WAI accessibility guidance
W3Schools accessibility tutorials
MDN Web Docs Originally published at Under The Hood. Get the next deep dive in your inbox: subscribe to Under The Hood.

How Browsers Implement Native Focus Rings and Their Accessibility Implications

Srikar Phani Kumar Marti — Mon, 27 Jul 2026 10:54:18 +0000

Ever had that moment when you tab through a form and suddenly the familiar glowing outline appears around a button or input? That subtle highlight, known as the native focus ring, feels so natural you barely notice it, until it’s missing or looks weird in your app.

I recently ran into a bug where my form’s custom styles completely hid the focus ring on keyboard navigation. Users relying on keyboards or assistive tech couldn’t tell which element was active. It was a small oversight but a huge accessibility problem.

Turns out, browser focus rings aren’t just a CSS border thrown on by default. There’s a surprising amount happening under the hood, different browsers paint focus rings differently, and customizing them can backfire if you don’t understand how browsers manage focus styles.

Let me walk you through how native focus rings work inside browsers, why they matter, the tricky tradeoffs when you override them, and some tips to debug focus visibility issues.

The moment focus rings became more than decoration

I was styling a login form and wanted a sleek look, so I removed the default outline:

input:focus, button:focus {
  outline: none;
}

Looks clean, right? But when I tried tabbing through the form, there was no visible focus indication. Keyboard users had no clue which field was active. Oops.

I tried adding my own focus style with a box-shadow but it looked inconsistent across browsers and sometimes disappeared if the element was disabled or hidden. That’s when I realized browser focus rings are more nuanced than I thought.

What actually triggers a native focus ring?

Native focus rings appear when an element receives focus via keyboard navigation, typically the Tab key. Browsers listen for input modality to decide whether to show the focus ring:

If you click an element with the mouse, many browsers suppress the focus ring to avoid distracting outlines.
If you tab into an element, the focus ring shows up to help keyboard users know where they are.

This behavior depends on the browser’s internal heuristics. Under the hood, browsers track the last input device (mouse, keyboard, touch) and conditionally render focus rings.

For example, Chrome uses an internal FocusRingController that listens for keyboard events and sets a flag enabling focus outlines only when appropriate.

How do browsers paint focus rings?

The exact rendering is browser-specific:

Chrome/Chromium: Uses a system-defined focus ring with a glowing blue outline by default. It’s typically a non-CSS painted layer.
Firefox: Paints a dotted or solid outline using CSS outline styles, but applies some default emphasis.
Safari: Uses a similar approach to Chrome but with different colors and thickness.

The focus ring isn’t just a simple CSS outline property. It can be an OS-level or browser-level visual effect that handles drawing and animation.

Why overriding focus rings can backfire

Many designers want to replace the native focus ring with a custom style that better fits their brand. That’s fine, but here’s the catch:

If you remove the native outline and don’t provide a visible replacement, keyboard users lose track.
Custom styles like box-shadow or border changes may not be accessible or consistent across zoom levels and high-contrast modes.
Some browsers disable focus rings if elements are disabled, or during certain animations.

For instance, I once tried this:

button:focus {
  outline: none;
  box-shadow: 0 0 5px 2px rgba(0, 150, 255, 0.7);
}

Looks nice until you zoom or switch to a high contrast theme. The shadow might be too subtle or get clipped by overflow.

The compromise: Use `:focus-visible` and respect user preferences

The :focus-visible pseudo-class is a game changer. It matches elements that should show focus rings based on the browser’s heuristics for input modality.

Instead of styling all :focus states, style only :focus-visible:

button:focus {
  outline: none;
}

button:focus-visible {
  outline: 2px solid Highlight;
  outline-offset: 2px;
}

This way, mouse clicks won’t trigger the outline, but keyboard navigation does.

Browsers also respect user preferences like prefers-reduced-motion and high contrast modes, so native focus rings adapt automatically.

Debugging focus ring issues in the wild

Sometimes your app still hides focus rings unexpectedly. Here’s how I debugged mine:

Inspect computed styles: The native ring often comes from outline or special browser painting. Check if outline: none is applied anywhere.
Check :focus-visible support: Not all browsers support it fully. For unsupported browsers, fallback to visible :focus styles.
Test keyboard navigation: Use Tab and Shift+Tab to cycle through elements and verify focus visibility.
Simulate different input modes: Chrome DevTools lets you force keyboard focus styles to test.
Look for clipping or overflow: Sometimes container elements with overflow: hidden clip the focus ring.

Wrapping up

Native focus rings are a subtle but vital piece of web accessibility. They’re more than just outlines, they’re signals to keyboard and assistive tech users about where they are in your UI.

Browsers make smart choices about when and how to show them based on input modality and user preferences. Overriding these styles is tempting but tricky; it’s easy to accidentally make your app less usable.

If you want custom focus styles, lean on :focus-visible and test thoroughly across devices and modes. And when in doubt, trust the browser’s native focus ring, it’s there for a good reason.

Next time you tab through a form, pause and appreciate the tiny glow that helps you navigate. It’s a quiet hero of accessibility, baked right into the browser’s core.

Helpful learning resources

W3C WAI accessibility guidance
W3Schools accessibility tutorials
MDN Web Docs Originally published at Under The Hood. Get the next deep dive in your inbox: subscribe to Under The Hood.

AI-Driven CSS Refactoring: When Generated Styles Surprise You

Srikar Phani Kumar Marti — Wed, 22 Jul 2026 10:41:39 +0000

Ever had that moment where you run an AI-powered CSS refactoring tool on your project hoping for a leaner stylesheet, and suddenly your carefully crafted grid breaks, animations stutter, or your page loads slower?

I’ve been there. You hand over your monolithic CSS file to an AI assistant, expecting magic. Instead, you get a mix of optimized selectors and some baffling new styles that don’t quite behave as expected.

Let me walk you through what’s really going on under the hood with AI-generated CSS, how these tools make decisions, and how you can spot and fix the surprises.

The bug that kicked off my curiosity

I was working on a client’s dashboard with a hefty CSS codebase. I tried out an AI tool that promised to refactor and optimize styles automatically. It scanned my styles, suggested removing unused rules, merging duplicates, and even replacing some properties for better performance.

But after applying the changes, a few widgets lost their alignment, some hover effects felt sluggish, and the page’s first paint was noticeably slower.

Why did this happen?

How AI tools generate and refactor CSS

Most AI-powered CSS tools start by parsing your existing styles into an internal representation, sometimes a CSS Object Model or an Abstract Syntax Tree. Then they apply heuristics or learned patterns to refactor:

Dead code elimination: Removing selectors or declarations that appear unused based on static analysis or runtime inspection.
Selector merging: Combining rules that share properties to reduce redundancy.
Property substitution: Replacing verbose or less performant CSS properties with more efficient alternatives.
Style simplification: Flattening deeply nested selectors or converting complex declarations into shorthand.

Some tools go further and generate styles from scratch based on component structure or design tokens, but that’s a bigger leap.

Performance optimization under the hood

When AI refactors CSS, it often targets performance by:

Reducing selector specificity: Complex selectors slow down the browser’s matching engine. AI might replace .nav > ul > li.active with simpler .nav-active classes.
Minimizing repaint and reflow triggers: Replacing properties like width with transform: scale() for animations, offloading work to the GPU.
Consolidating styles: Reducing the total CSS file size to speed up download and parse times.

But these changes rely on assumptions about your markup and runtime behavior. That’s where surprises emerge.

The tradeoff between automation and manual control

AI tools can save hours of mechanical refactoring, especially in large legacy codebases. But they don’t know your intent, context, or user experience priorities.

For example, simplifying selectors might break edge cases where styles depend on DOM hierarchy. Removing unused styles based on static analysis might miss dynamic classes applied by JavaScript.

You lose some manual control and have to verify every change carefully.

Debugging unexpected regressions

When the AI-generated CSS causes layout shifts or performance regressions, here’s how I debug:

Compare before/after CSS snapshots. Use diff tools to spot what rules were removed or altered.
Check runtime classnames. Inspect the live DOM to confirm if classes expected by the new CSS actually appear.
Profile paint and layout. Use browser devtools to see if new styles trigger expensive repaints or layout thrashing.
Test interaction states. Hover, focus, active states often get overlooked if AI removes pseudo-classes.
Revert selectively. Roll back refactoring in chunks to isolate problematic changes.

These steps helped me catch cases where AI replaced position: absolute with position: relative assuming simplification, breaking overlays.

Using AI CSS tools effectively

Here are some practical tips if you want to harness AI for CSS refactoring without headaches:

Use on isolated components first. Experiment on small parts of your UI to understand AI’s patterns.
Combine with unit and visual regression tests. Automated tests catch unintended style changes early.
Review generated CSS manually. Don’t blindly trust AI output, look for surprising selectors or missing properties.
Keep backups before applying. So you can revert if layout breaks.
Configure AI tool options. Some allow toggling aggressive optimizations or preserving specific selectors.

When to trust AI vs. when to code by hand

If your project has:

Stable, well-documented CSS architecture: AI can assist safely.
Dynamic, JS-driven styling: Be wary. AI might miss runtime-dependent classes.
Performance bottlenecks in CSS: AI-generated simplifications may help, but test thoroughly.

Ultimately, AI is a powerful assistant, not a replacement for CSS expertise. It’s like having a junior developer who tries to clean up your styles but doesn’t know the edge cases yet.

Wrapping up

AI-driven CSS refactoring is exciting and promising, but it comes with tradeoffs. Understanding how these tools analyze and rewrite your styles lets you anticipate issues, debug faster, and keep control over your UI’s look and feel.

Next time you run an AI CSS tool, remember: it’s not magic. It’s pattern recognition and heuristics that sometimes need your human judgment to shine.

Helpful learning resources

W3C WAI accessibility guidance
W3Schools accessibility tutorials
MDN Web Docs Originally published at Under The Hood. Get the next deep dive in your inbox: subscribe to Under The Hood.

Debugging AI Model Integration Latency in Frontend: Frontend Architecture and UX Trade-offs

Srikar Phani Kumar Marti — Tue, 21 Jul 2026 11:08:17 +0000

I remember the first time I dropped a client-side AI model into a web app. The feature was cool: users could upload text, get instant AI-powered insights, all running in the browser without server roundtrips.

But then the complaints started. "Why is the UI freezing when I type?" "The spinner stays forever!" "It feels slow and unresponsive."

I’d built fast React apps before, but this was different. The AI model was a beast: it hogged CPU, blocking the main thread. The loading states were clunky. And debugging the latency wasn’t straightforward.

If you’re integrating AI models directly in the frontend , whether with TensorFlow.js, ONNX.js, or WebAssembly-powered inference , you’ve probably faced this too. It’s not just about model size. It’s about how your frontend architecture manages loading, responsiveness, and UX feedback.

Let me walk you through what I learned debugging and fixing AI integration latency on the frontend.

The typical bottleneck: AI models block the main thread

When you run an AI model in the browser, it’s usually CPU-heavy and synchronous. Imagine this: a user triggers inference by clicking a button. Your JS calls the model’s predict function. The browser’s main thread is tied up for hundreds of milliseconds or even seconds.

During that time, the UI can’t respond , no animations, no input updates, no spinner updates. It feels frozen.

The naive approach is:

function handlePredict() {
  setLoading(true); // show spinner
  const result = model.predict(inputData); // blocks main thread
  setResult(result);
  setLoading(false);
}

But model.predict runs synchronously and hogs the main thread. React can’t update the spinner because it won’t get CPU cycles until predict finishes.

So your spinner either never shows or shows after the blocking finishes, confusing users.

Architecting for non-blocking AI inference

The key is to never block the main thread. If the model API is synchronous, you can’t just call it directly in a React event handler.

Here are some options:

1. Offload to Web Workers

Web Workers run in a separate thread. If you move model inference there, your main UI thread stays responsive.

This means:

Create a worker script that loads the AI model.
Use postMessage to send input data and receive results asynchronously.
Update React state only when the worker responds.

Example:

// main thread
worker.postMessage({ input: inputData });
worker.onmessage = (e) => {
  setResult(e.data.result);
  setLoading(false);
};
setLoading(true);

This solves blocking but adds complexity: worker lifecycle, message serialization, and model loading duplication.

2. Break inference into chunks

Some models can run inference in smaller steps or batches. Using requestIdleCallback or scheduling microtasks lets you chunk work so the UI gets breathing room.

This is advanced and depends on model API support.

3. Lazy load and cache models

Loading a model can be slow too. Lazy load models only when needed to avoid upfront delays.

Cache the model instance so repeated inference calls don’t reload weights.

UX tradeoffs: Loading states and perceived performance

Showing a spinner during inference is basic but often broken if blocking happens synchronously.

Instead, consider:

Optimistic UI: Show preliminary results or placeholders immediately.
Progressive feedback: If inference takes >200ms, show a subtle loading indicator.
Disable input: Prevent further input during inference to avoid confusion.
Timeouts and cancelation: Allow users to cancel long-running inference.

For example, I replaced the spinner with a dimmed overlay and a "Thinking..." message that only appears if inference crosses 300ms. This avoids flicker for fast runs.

Debugging slow or blocking AI features

Here’s how I tracked down what was blocking:

Chrome DevTools Performance tab: Record a profile during inference. Look for long tasks blocking the main thread.
Flame charts: Identify the model.predict call and see how long it takes.
Check React DevTools: See if state updates or renders are delayed.
Network tab: Confirm model weights aren’t repeatedly fetched.

After profiling, I found the model’s predict took 600ms on a typical input, blocking React’s render updates.

Putting it all together: a practical example

function AIComponent() {
  const [loading, setLoading] = React.useState(false);
  const [result, setResult] = React.useState(null);
  const workerRef = React.useRef(null);

  React.useEffect(() => {
    workerRef.current = new Worker('./aiWorker.js');
    workerRef.current.onmessage = (e) => {
      setResult(e.data.result);
      setLoading(false);
    };
    return () => workerRef.current.terminate();
  }, []);

  function handlePredict(inputData) {
    setLoading(true);
    workerRef.current.postMessage({ input: inputData });
  }

  return (
    <div>
      <Input onChange={handlePredict} disabled={loading} />
      {loading && <p>Running AI model...</p>}
      {result && <ResultDisplay data={result} />}
    </div>
  );
}

The worker script (aiWorker.js) handles loading the model once and runs inference asynchronously.

Final thoughts

Integrating AI models on the frontend isn’t plug-and-play. When your model hogs the main thread, the whole UX suffers.

Your best bet:

Use Web Workers or similar off-main-thread mechanisms.
Carefully design loading states to avoid flicker and freezing.
Debug with profiling tools to spot blocking tasks.
Lazy load and cache models to avoid repeated delays.

With these, your AI feature won’t just work, it’ll feel smooth and responsive , which is what your users really care about.

Helpful learning resources

MDN Web Docs
web.dev performance guidance
React documentation Originally published at Under The Hood. Get the next deep dive in your inbox: subscribe to Under The Hood.

How React Fiber Handles High Priority Updates: Insights and Debugging Techniques

Srikar Phani Kumar Marti — Mon, 20 Jul 2026 10:48:12 +0000

You know that annoying moment when you type into a React input field, but the UI lags, or your app feels sluggish? Maybe your keystrokes delay, buttons take a beat to respond, or animations stutter. You wonder, “Is React blocking the main thread here?”

Turns out, React Fiber is working hard behind the scenes to keep your app responsive by juggling update priorities. But this juggling act can sometimes trip you up with weird bugs or race conditions.

Let’s pull back the curtain on React Fiber’s update prioritization, how it interrupts work for urgent updates, and what you can do to debug when your UI feels off.

The moment React Fiber kicked in for me

It happened while building a complex form. I noticed that when I typed in a text input, the cursor would jump or freeze briefly. Meanwhile, a heavy animation or a slow state update elsewhere in the app seemed to be hogging the frame. I assumed React was just slow.

Digging into React DevTools scheduler flamegraphs, I saw something surprising. React was actually pausing the animation work to prioritize handling my input update. But sometimes the cursor issue still happened.

Why? Because Fiber’s priority system is sophisticated but not magic. It tries to interrupt low priority tasks to let urgent updates run sooner, but the way you schedule updates and side effects can still cause weird glitches.

React Fiber’s priority lanes: the secret sauce

React Fiber breaks down updates into "lanes", think of lanes as buckets for different priority levels. Some lanes are for urgent work like user input or animations; others are for less urgent things like data fetching or rendering big lists.

When a high priority update comes in, say a keystroke, Fiber tries to pause or interrupt lower priority lanes to process the input immediately. This keeps your UI feeling snappy.

Here’s a simplified example:

Discrete updates: Typing, clicks , highest priority
Continuous updates: Mouse movement, scroll events , high priority
Default updates: Normal renders, data loading , low priority

Fiber’s scheduler assigns each update to the right lane and schedules work accordingly.

Interrupting work: how Fiber preempts lower priority updates

Imagine React is mid-rendering a big, slow component update when you suddenly type a character. Without interruption, your UI would lag until that render finishes.

Fiber’s scheduler watches for higher priority updates and can pause or even abandon the ongoing render. It keeps track of which lanes are currently being worked on and which are pending.

This means your typing causes React to:

Mark the current render as interruptible.
Push the typing update into a high priority lane.
Stop the low priority render.
Start rendering the typing update immediately.

Once done, React can resume or restart the low priority work later.

Why you still see jank or race conditions

Even with this system, you can hit rough edges:

State updates batching: If you batch low and high priority updates together, React may delay the urgent ones.
Synchronous updates: For example, legacy event handlers using flushSync can block the scheduler.
Expensive effects: Heavy useEffect or layout effects running synchronously after commit can block the main thread and cause lag.
Race conditions: When multiple updates with different priorities modify the same state, you might see flickering or stale renders.

Debugging high priority update issues

Here’s what helped me track down and fix these issues:

1. Use React DevTools Profiler with Scheduler Tracing

React DevTools lets you see which updates ran, their priority lanes, and how long they took.

Look for:

Updates that take too long
High priority updates queued behind low priority work
Frequent interruptions or restarts

2. Avoid mixing priorities in the same state update

If you update state in response to both user input and background tasks, split them into separate states or use startTransition for low priority updates.

Example:

const [text, setText] = useState('');

function onChange(e) {
  setText(e.target.value); // High priority update
  startTransition(() => {
    // Low priority background update
    fetchSuggestions(e.target.value);
  });
}

3. Don’t block the main thread in effects

Heavy computations inside useEffect or useLayoutEffect can block React’s ability to handle urgent updates. Offload these to Web Workers or throttle them.

4. Use `flushSync` sparingly

Calling flushSync forces React to synchronously flush updates, which can block the scheduler and hurt responsiveness.

5. Test with `React.StrictMode` and Concurrent Features

StrictMode double-invokes some lifecycles to help spot bugs. Using React’s experimental Concurrent Mode gives you a sneak peek at how Fiber handles priorities.

Putting it all together: what I learned

React Fiber’s update prioritization is a well-crafted system to keep your app responsive by juggling multiple lanes of work. It tries to let urgent updates like user input interrupt slower renders.

But it’s not magic. Your code’s update patterns, side effects, and batching choices impact how well this prioritization works.

When you feel jank or see race conditions, think about how your updates flow through Fiber’s lanes. Use DevTools to peek under the hood. Split high and low priority work, avoid blocking the main thread, and respect the scheduler’s heuristics.

Next time your React app feels sluggish or your cursor jumps, you’ll know where to look and how Fiber is trying to keep things smooth under the hood.

Helpful learning resources

MDN Web Docs
web.dev performance guidance
React documentation Originally published at Under The Hood. Get the next deep dive in your inbox: subscribe to Under The Hood.

React Architecture Beyond Components: Understanding Context, Hooks, and Render Phases

Srikar Phani Kumar Marti — Fri, 17 Jul 2026 11:46:09 +0000

You know that feeling when your React app suddenly behaves weirdly , state seems stale, effects run twice, or context values don’t update where you expect?

I’ve been there. That subtle bug where your component reads an outdated context value or a hook’s state seems frozen until you refresh. Turns out, to really understand and debug these issues, you need to peek under React’s hood.

Not just at components, but at how React schedules rendering phases, manages context propagation, and runs hooks.

The familiar headache: stale context or state inside hooks

Imagine this: you have a ThemeContext with a mode string that toggles between "light" and "dark".

const ThemeContext = React.createContext('light');

function ThemedButton() {
  const theme = React.useContext(ThemeContext);
  React.useEffect(() => {
    console.log('Theme changed to', theme);
  }, [theme]);
  return <button className={theme}>Click me</button>;
}

You toggle the theme in a parent provider, and expect the button to update and log the new theme immediately. But sometimes, your console shows the old theme or the effect runs with the previous theme value.

What’s going on?

React’s render phases: the secret to consistency

React doesn’t just call your components and hooks once per update. Behind the scenes, it runs multiple render phases:

Render phase: React calls your components purely to figure out what the UI should look like. No DOM mutations happen here , it’s a dry run.
Commit phase: React applies changes to the DOM and runs effects.

This separation exists so React can pause, restart, or even abandon work (especially in Concurrent Mode).

Context propagation in render phase

Context values flow down the tree during render. When a provider’s value changes, React marks consumers to update. But each render phase captures the context value at that moment.

If React tries rendering a component multiple times in quick succession (say, because of a higher priority update), that component’s hook calls may see different context values over time.

Hooks and render phase interaction: why state and effects feel out of sync

Hooks like useState and useEffect behave differently in render vs commit phases:

useState returns the current state as of the latest committed render.
useEffect runs after the commit phase.

So, if React re-renders a component multiple times before committing, your hooks see the state and context values for that particular render phase, even if they change in the next render.

This is why sometimes your effect logs or runs with a "stale" value , it’s tied to the value React had during the render phase that triggered the effect.

A concrete example: a double render mystery

Say React schedules a low-priority update to toggle a context value. During the render phase, it attempts the update but then pauses to process a higher-priority event. It discards the intermediate render and restarts.

Your component’s hooks ran twice:

First with context value A.
Then again with the new context B.

But only the second render commits. Effects run with B. Yet if you have logging inside your render logic, you might see both A and B , confusing!

Why this matters for debugging

When you see weird state or context inconsistencies:

Remember React might be calling your components multiple times before committing.
Side effects inside render (like logging or fetches) can run multiple times unexpectedly.
Your hooks’ dependencies might need careful attention to avoid stale closures.

Tips for taming render phase quirks

Avoid side effects in render. Keep render pure. Move logic into useEffect or callbacks.
Memoize context values in providers to avoid unnecessary re-renders.
Use useCallback and useMemo to stabilize dependencies.
Understand your React version: Concurrent Mode brings more render phase interruptions.

Wrapping up

React’s internal dance between context, hooks, and render phases is what keeps your UI consistent , but it also means you occasionally get surprising behavior.

Next time your component seems to have stale state or effects run oddly, remember: React might be rendering more than once before it commits. Knowing this changes how you think about hooks and context and helps you debug those tricky lifecycle bugs.

Keep poking under the hood. React’s magic is complicated , but once you get the mechanics, it feels a lot less like magic and a lot more like a manageable machine.

Helpful learning resources

W3C WAI accessibility guidance
W3Schools accessibility tutorials
MDN Web Docs Originally published at Under The Hood. Get the next deep dive in your inbox: subscribe to Under The Hood.

Debugging React Context Performance Issues: When and Why Components Re-render

Srikar Phani Kumar Marti — Thu, 16 Jul 2026 11:34:11 +0000

Ever had this happen? You change a value in your React Context Provider, expecting just a few components to update. But suddenly, half your app re-renders, and your performance tanks. You scratch your head and wonder: why is React context so slow? I’ve been there. This article pulls back the curtain on React Context's update mechanism, why components re-render aggressively, and how to tame the beast.

The React Context gotcha: Every consumer re-renders on update

Imagine you have a ThemeContext with a theme value (say, "light" or "dark"). You wrap your app:

<ThemeContext.Provider value={theme}>
  <App />
</ThemeContext.Provider>

Now, anywhere you call useContext(ThemeContext), React will re-render that component every time the value changes.

Sounds obvious? The surprise is that React does not do a deep comparison on the context value. It just checks if the reference changed (with Object.is). So if you provide a new object or primitive value, all consumers re-render.

Here’s the kicker: even if your components only use part of the context, or even if the value they read is unchanged inside a new object, they still re-render.

Why React doesn’t do partial updates inside context

React Context is designed as a simple pub-sub model: context value changes notify all consumers. React doesn’t track which consumer reads which part of the context value , it can’t know which slice matters to a component without explicit help.

Under the hood, when the provider’s value changes (meaning the reference changes), React triggers an update for every subscribed consumer. This is a fast operation for a handful of components, but not when your context is huge or used widely.

Common anti-patterns that cause unnecessary re-renders

1. Passing inline objects or functions as `value`

Developers often write:

<ThemeContext.Provider value={{ theme, toggleTheme: () => setTheme(t => t === 'dark' ? 'light' : 'dark') }}>

This creates a new object and a new function on every render, so the context value changes every time, even if theme is the same.

Fix: Memoize the value with useMemo and functions with useCallback.

const toggleTheme = useCallback(() => {
  setTheme(t => t === 'dark' ? 'light' : 'dark')
}, [])
const value = useMemo(() => ({ theme, toggleTheme }), [theme, toggleTheme])

<ThemeContext.Provider value={value}>
  ...
</ThemeContext.Provider>

2. Using one big context for many unrelated values

Storing lots of state in a single context causes any change to trigger re-renders everywhere. For example, a context with { user, theme, settings, notifications } means a theme change re-renders components that only care about user.

Fix: Split your context into multiple smaller contexts, each responsible for a specific piece of state.

3. Deeply nested consumers that don’t memoize

If you use useContext inside deeply nested components without memoization, you may get more re-renders than necessary.

Fix: Use React.memo or useMemo to avoid re-renders when props or context values haven’t changed.

Profiling context-related re-renders

React DevTools Profiler is your friend here.

Start recording.
Trigger your context update.
Look for components that re-render unexpectedly.

You’ll often notice many components updating even if they don’t use the changed part of the context.

How React Context actually triggers updates

Under the hood, React keeps a linked list of all consumers subscribed to the provider. When the context value changes:

React compares the new value with the old reference using Object.is.
If they differ, React schedules an update for all consumers.
Each consumer re-renders and reads the new context value.

There is no built-in mechanism to track which consumers care about which parts of the value.

Alternatives and patterns to optimize context usage

Use multiple contexts

Split your state across several contexts. For example:

UserContext
ThemeContext
SettingsContext

This way, updating theme won’t cause user-related components to re-render.

Use selectors with `useContextSelector` (third-party)

Libraries like use-context-selector let you subscribe to specific slices of context values, so components re-render only when their selected slice changes.

Example:

const theme = useContextSelector(ThemeContext, ctx => ctx.theme)

Only components whose selected slice changes will re-render.

Lift state closer to where it’s needed

Sometimes, context is used for convenience but state can live closer to components that need it, reducing unnecessary propagations.

Memoize components and values

Use React.memo, useMemo, and useCallback to avoid re-renders caused by changing references.

When context re-renders are unavoidable

Sometimes, your app is small enough or updates infrequent enough that simple memoization suffices. Premature optimization adds needless complexity.

But if you spot lag, jank, or excessive re-renders tied to context, start here:

Profile with React DevTools
Check your context value references
Split contexts
Use selectors if needed

Wrapping up

React Context is incredibly useful but comes with this gotcha: any change to the context value triggers all consumers to re-render.

Understanding this helps you avoid performance pitfalls and write snappy apps. Next time your context update slows things down, you’ll know exactly where to look and what to fix.

Helpful learning resources

MDN Web Docs
web.dev performance guidance
React documentation Originally published at Under The Hood. Get the next deep dive in your inbox: subscribe to Under The Hood.

HTTP QUERY is here: what changes for frontend data fetching?

Srikar Phani Kumar Marti — Wed, 15 Jul 2026 11:22:57 +0000

You’ve probably hit this frustrating moment: your frontend needs to fetch data with complex filters or queries, but GET just won’t cut it because your URL grows unwieldy or exceeds length limits. So you switch to POST, shove your JSON search parameters in the body, and call it a day.

Except now your POST request is meant to be a safe, read-only fetch. But HTTP semantics say POST is neither safe nor idempotent. That kills caching on CDNs, disables certain browser optimizations, and confuses intermediaries. You’re stuck in a weird limbo.

Enter HTTP QUERY , the new kid on the block, standardized by RFC 10008 in June 2026. It's safe and idempotent like GET but also lets you send a request body like POST. Sounds like the best of both worlds, right? Let’s dig into what this means for frontend data fetching and why you probably shouldn’t just flip the switch on all your POST /search routes tomorrow.

What is HTTP QUERY, exactly?

HTTP QUERY is a new request method defined to address a long-standing gap: how to send complex, structured queries in a safe, cacheable way.

GET requests are safe and idempotent, which means they’re perfect for fetching data. But their parameters live in the URL, which has length limits (around 2000 characters in many browsers) and poor ergonomics for deeply nested or complex JSON-like filters.

POST requests let you send a rich body but are considered unsafe and non-idempotent by default. This kills caching on the CDN and browser layers, since intermediaries assume POST changes server state.

HTTP QUERY combines the best of both:

It’s safe and idempotent, so intermediaries treat it like GET.
It supports a request body, so you can send complex JSON queries without cramming them into a URL.
It keeps your URLs clean and uncluttered.

Why does safe + body matter?

The HTTP spec has historically struggled with this. Safe methods (GET, HEAD) can’t have bodies according to some interpretations, so complex queries get shoved into URLs or POST bodies.

That leads to practical downsides:

Cache busting: CDNs and browsers ignore POST responses for caching, even when you know the request is read-only.
Proxy confusion: Intermediaries treat POST as a possible state-changing method, so they don’t optimize or retry it safely.
Developer confusion: You have to choose between semantic correctness and practical needs.

HTTP QUERY says: let’s have a safe, idempotent method that supports bodies, so everyone knows it’s a read-only fetch with complex input.

What does this mean for frontend data fetching?

Complex search filters get a first-class home

Say you’re building a search UI with filters like date ranges, nested facets, or fuzzy matching. Encoding these in query strings quickly becomes a nightmare:

/search?dateFrom=2024-01-01&dateTo=2024-01-31&filter[category]=books&filter[price][min]=10&filter[price][max]=50

Ugly, error-prone, and brittle. Plus, some browsers or proxies might truncate the URL.

With HTTP QUERY, you can move this entire JSON payload into the request body cleanly:

QUERY /search HTTP/1.1
Content-Type: application/json

{
  "dateFrom": "2024-01-01",
  "dateTo": "2024-01-31",
  "filter": {
    "category": "books",
    "price": { "min": 10, "max": 50 }
  }
}

This keeps your URLs short and your request format consistent.

GraphQL-style queries get a simpler transport

GraphQL requests often use POST because their queries live in the body. But that means you lose GET semantics, caching, and some CDN optimizations.

HTTP QUERY lets you send a GraphQL query in the body while keeping the request safe and idempotent, opening doors for better caching.

Caching and CDN behavior improve

Because HTTP QUERY is explicitly safe and idempotent, CDNs and browsers can cache these requests like GETs. That means:

Edge caches serve responses faster
Reduced server load
Better offline and retry behavior

But this depends on your CDN and browser supporting HTTP QUERY correctly , which is still a work in progress.

Browser and framework support is still catching up

As of mid-2026, HTTP QUERY is brand new. Most browsers have started to support it at the network level, but APIs like fetch() and XMLHttpRequest are still rolling out support.

Frameworks, HTTP clients, and intermediaries (proxies, CDNs) also need updates:

fetch(): New versions accept method: 'QUERY'.
Axios, superagent: Libraries need to add explicit support.
CDNs: Providers must recognize QUERY as safe and cacheable.

Until then, you may need fallbacks or polyfills.

Why you shouldn’t blindly replace all POST /search calls

It’s tempting to think: "Great, HTTP QUERY solves all my problems, I’ll just swap POST for QUERY everywhere!"

But hold your horses:

Some POST /search endpoints trigger server-side side effects or logging that aren’t safe. Changing method semantics without audit risks bugs.
Caching behavior depends on correct cache headers and CDN support; otherwise, you might see stale data or cache misses.
Client and server libraries need to handle QUERY correctly, or you’ll get unexpected failures.
Browsers and older environments might reject unknown methods or fail silently.

Best practice? Use HTTP QUERY for new endpoints designed for safe, read-only queries with complex bodies. For existing POST endpoints, evaluate method semantics carefully before switching.

How to experiment with HTTP QUERY today

Check your HTTP clients: Try fetch('/search', { method: 'QUERY', body: JSON.stringify(payload) }) in browsers with up-to-date support.
Update your backend: Make your server recognize and handle QUERY requests like GET but parse the body.
Test CDN behavior: Confirm your edge cache treats QUERY like GET for caching.
Monitor fallbacks: Have fallbacks to POST or GET for clients or intermediaries lacking support.

What I learned debugging QUERY support in my apps

I tried switching a complex filter endpoint from POST to QUERY in a staging app. It was smooth on the server side , minimal code changes. But the frontend fetch calls failed in older browsers. My CDN ignored QUERY requests initially, so no caching kicks in.

Adding a feature detection layer and a fallback to POST for unsupported clients fixed the problem. Also, ensuring my server sent proper Cache-Control headers was critical to leverage caching.

This showed me HTTP QUERY is promising but still early-stage. You’ll want to adopt gradually and monitor carefully.

So is HTTP QUERY the future?

It feels like a neat, principled way to fix a longstanding HTTP awkwardness. For frontend devs wrestling with complex read-only queries, it means cleaner URLs, better caching, and clearer semantics.

But like any new protocol feature, it needs ecosystem support, adoption, and time to mature.

In the meantime, keep using POST for complex queries when needed, but watch HTTP QUERY’s progress. When tooling and infrastructure are ready, it’ll be a handy tool in your data fetching toolbox.

And if nothing else, it’s nice to see the web’s foundations still evolving , one tiny method at a time.

Originally published at Under The Hood.

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New Newsletter Alert: Under The Hood Has a New Home

Srikar Phani Kumar Marti — Tue, 14 Jul 2026 10:49:57 +0000

I have wanted this one to feel a little loud, so here it is: Under The Hood has a new home.

For a while, I was publishing on Substack. It was convenient, familiar, and honestly a pretty good place to get started. But at some point I wanted the newsletter to feel more like mine. Not just another page inside someone else's platform, but a real owned space where the archive, design, subscribers, and publishing flow all live together.

So I moved.

I ported my old Substack posts into this new newsletter, and that turned out to be more interesting than I expected. There is something weirdly satisfying about watching an archive move from one system into another: titles, dates, cover images, old essays, little formatting quirks, all of it getting cleaned up and finding a new shape. It felt less like a migration and more like unpacking boxes after moving into a new place.

The stack is intentionally simple:

Next.js for the site and admin workflow
Postgres on Neon for posts, subscribers, publishing state, and platform records
Prisma for the database layer
Resend for newsletter email flows
Vercel for hosting
A small private admin app for drafting, publishing, syndication, and notifications

There is also a lightweight content pipeline behind the scenes, mostly so I can keep the writing process organized: ideas, drafts, publishing status, platform links, and the occasional reminder when something needs attention. I do not want the tooling to become the story, but I do want the system to make publishing easier to keep doing.

And that is the big difference between building a custom newsletter and just posting on LinkedIn or another feed.

A social post is borrowed attention. It can travel fast, but it lives inside someone else's rules, ranking system, and interface. A newsletter and owned archive are slower in a good way. They are easier to return to. They are easier to search. They can have their own voice, structure, and rhythm. They do not disappear into the feed ten minutes after you publish them.

I will still post on LinkedIn and other platforms when it makes sense. Those places are useful for discovery. But this site is the source of truth now. The full essays live here. The archive lives here. The subscriber list starts here.

That feels right.

This first post is mostly a marker in the ground: the new newsletter is live, the old posts have been moved over, and the next batch of writing starts from here.

If you have suggestions for what I should write next, or if there is something from the old Substack archive you want me to revisit, please leave a comment wherever you found this post or send the suggestion my way. I am going to start building the next backlog from here.

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Originally published at Under The Hood.

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DEV Community: Srikar Phani Kumar Marti

Debugging Complex Pointer and Touch Event Interactions in Mobile Browsers

The moment things got weird: touch events firing but pointer events missing

Why event sequences differ so much on mobile

The tricky default behaviors and event.preventDefault()

Common pitfalls with custom gesture recognizers

How I debugged these issues in DevTools

A concrete example: building a horizontal swipe recognizer that doesn’t block vertical scroll

Wrapping up

Helpful learning resources

React Concurrent Rendering: Scheduling, Interruptions, and Debugging Suspense Boundaries

React’s concurrent rendering scheduler: what’s it really doing?

What happens when Suspense enters the scene?

How React prioritizes and interrupts updates

Why does Suspense sometimes unexpectedly remount or reset state?

Debugging Suspense boundaries in production

Practical tips to reduce flickers and interruptions

When you want to dive deeper into the scheduler

Helpful learning resources

How Browsers Handle Keyboard Events: From Raw Input to DOM Events

When you press a key, the OS speaks first

The browser’s input pipeline: raw event to DOM event

Key repeat

Composition events for IMEs

Order matters: event sequence and quirks across browsers

Practical debugging tips

Why your input bugs might be composition bugs

Wrapping up

Helpful learning resources

Screen Reader Handling of ARIA Live Regions: Timing, Interruptions, and Debugging

The weird silence: live region updates don’t always get announced

How screen readers process ARIA live regions

The problem with rapid updates and DOM mutations

Interruptions: how user focus and speech affect announcements

Debugging live region announcements

Under the hood: what you can do to improve live region reliability

A concrete example: reliable live region updates in a SPA

Why this still isn’t perfect

What I wish I knew sooner

Helpful learning resources

How Browsers Implement Native Focus Rings and Their Accessibility Implications

The moment focus rings became more than decoration

What actually triggers a native focus ring?

How do browsers paint focus rings?

Why overriding focus rings can backfire

The compromise: Use :focus-visible and respect user preferences

Debugging focus ring issues in the wild

Wrapping up

Helpful learning resources

AI-Driven CSS Refactoring: When Generated Styles Surprise You

The bug that kicked off my curiosity

How AI tools generate and refactor CSS

Performance optimization under the hood

The tradeoff between automation and manual control

Debugging unexpected regressions

Using AI CSS tools effectively

When to trust AI vs. when to code by hand

Wrapping up

Helpful learning resources

Debugging AI Model Integration Latency in Frontend: Frontend Architecture and UX Trade-offs

The typical bottleneck: AI models block the main thread

Architecting for non-blocking AI inference

1. Offload to Web Workers

2. Break inference into chunks

3. Lazy load and cache models

UX tradeoffs: Loading states and perceived performance

Debugging slow or blocking AI features

Putting it all together: a practical example

Final thoughts

Helpful learning resources

How React Fiber Handles High Priority Updates: Insights and Debugging Techniques

The moment React Fiber kicked in for me

React Fiber’s priority lanes: the secret sauce

Interrupting work: how Fiber preempts lower priority updates

Why you still see jank or race conditions

Debugging high priority update issues

1. Use React DevTools Profiler with Scheduler Tracing

2. Avoid mixing priorities in the same state update

3. Don’t block the main thread in effects

4. Use flushSync sparingly

The compromise: Use `:focus-visible` and respect user preferences

4. Use `flushSync` sparingly

5. Test with `React.StrictMode` and Concurrent Features

1. Passing inline objects or functions as `value`

Use selectors with `useContextSelector` (third-party)