How I Built a Free Browser-Based Monitor Testing Tool with Astro

Daniel Park — Mon, 23 Mar 2026 05:00:46 +0000

A few months ago, I bought a new monitor. Like any careful buyer, I wanted to check it for dead pixels, backlight bleed, and color accuracy before the return window closed.

I searched online for a tool. What I found was frustrating — every tool only did one thing. One site tested dead pixels. Another was just a black screen for backlight bleed. Color accuracy tests were on yet another domain. None of them worked well on mobile. Most had intrusive ads that defeated the purpose of a "full screen" test.

So I built DisplayMaster — a free, all-in-one browser-based monitor testing tool. No downloads. No sign-up. Just open and test.

What It Does
DisplayMaster covers the three most important monitor quality checks:

🔴 Dead Pixel Detection
Cycles through solid color screens — red, green, blue, white, and black — to help you spot stuck or dead pixels instantly. Dead pixels appear as dots that don't change color when the background does.

💡 Backlight Bleed Test
Displays a full black screen. In a darkened room, any uneven glow around the edges reveals backlight bleeding — a common issue with IPS and VA panels.

🎨 Color Accuracy Test
Renders gradient and solid color patches to help verify color uniformity across your display. Essential for designers and video editors who need accurate color reproduction.

Why Astro?
I chose Astro for a few key reasons:

Zero JS by default. A monitor testing tool is fundamentally a display tool — it needs to render full-screen color blocks as fast as possible. Astro's island architecture means I ship zero JavaScript unless I explicitly opt in. The result is a near-instant page load even on slow connections.

File-based routing. Each test mode (/dead-pixel, /backlight-test, /color-test) maps to a clean route with no configuration overhead.

Static output + edge deployment. Astro's static build output pairs perfectly with Cloudflare Pages. Every deploy is a global CDN push — no server, no cold starts, no cost.

Here's a simplified version of how the dead pixel test component works:

---
const colors = ['#FF0000', '#00FF00', '#0000FF', '#FFFFFF', '#000000'];
let current = 0;
---

<div id="test-screen" style={`background: ${colors[current]}; width: 100vw; height: 100vh;`}>
  <button onclick="nextColor()">Next Color</button>
</div>

<script>
  const colors = ['#FF0000', '#00FF00', '#0000FF', '#FFFFFF', '#000000'];
  let current = 0;

  window.nextColor = () => {
    current = (current + 1) % colors.length;
    document.getElementById('test-screen').style.background = colors[current];
  }

  // Click anywhere to advance
  document.getElementById('test-screen').addEventListener('click', nextColor);
</script>

The entire interaction is a single event listener and an array. No framework overhead needed.

The Tech Stack
Layer Tool
Framework Astro
Hosting Cloudflare Pages
Version control GitHub
AI coding assist opencode
Analytics Cloudflare Analytics
Total monthly cost: $0. This is the indie maker dream stack.

What I Learned
Full-screen API matters more than I thought.
Getting a truly full-screen experience across different browsers required careful handling of the Fullscreen API with vendor prefixes. Safari in particular has quirks with webkitRequestFullscreen that took a while to iron out.

Users arrive with very specific intent.
People searching "dead pixel test" or "backlight bleed check" know exactly what they want. That shaped how I structured the navigation — get out of the way, and let the user start the test in one click.

Static doesn't mean dumb.
I initially worried that a static Astro site couldn't handle the interactive parts. Turns out, for a tool like this, a few sprinkles of vanilla JavaScript is all you need. The simplicity is a feature, not a limitation.

What's Next
Remote testing mode — share a link that opens a specific test on any screen

Test report generation — export a PDF summary of test results

More color patterns — ANSI color bars, gradient sweeps, and checker patterns for advanced calibration

👉Try It

It's completely free. If you've just bought a new monitor, give it a spin — it takes less than 2 minutes to run all three tests.

If you find it useful (or find a bug), I'd love to hear from you. Drop a comment below or find me on X: @urblessedman

Built with Astro. Deployed on Cloudflare Pages. Inspired by the frustration of buying a new monitor.

DEV Community: Daniel Park

How I Built a Free Browser-Based Monitor Testing Tool with Astro