DEV Community: Md Shohan

7 Free Browser-Based Encryption Tools Built on the Web Crypto API (Nothing Gets Uploaded)

Md Shohan — Mon, 19 Oct 2026 11:01:12 +0000

Handing a sensitive file to an online tool usually means handing it to that tool's server first. For a PDF converter that's an annoyance. For a private key, a certificate request or an encrypted backup, it's a real problem.

We built the Encryption & Keys category on Utility Tools Lab around the opposite assumption: the work should happen in your browser, using the Web Crypto API, and nothing should be transmitted. It has 7 free tools. Here's what each does and how it's built.

Encrypt files and text

AES File Encryptor
Encrypt or decrypt any file with a passphrase using AES-256-GCM, entirely in your browser. The key is derived from your passphrase with PBKDF2, run 250,000 times over. Encryption uses AES-GCM, which is authenticated, so a wrong passphrase produces a clear failure rather than silently garbled bytes.

AES Text Encryptor
The same AES-256-GCM and PBKDF2 approach for text strings. The output is a portable Base64 string, so you can paste it into a note, a chat or a config file and decrypt it later with the same passphrase.

Generate key pairs

RSA Key Generator
Generate RSA key pairs at 2048, 3072 or 4096 bits, for encryption (OAEP) or signing (PSS), in PEM format. Download or copy instantly.

ECDSA Key Generator
Generate ECDSA or ECDH key pairs on P-256, P-384 or P-521, in PEM or JWK format. The private key is blurred by default.

Between them these two cover the main asymmetric families: RSA for legacy compatibility, and elliptic curves for modern TLS, JWT and code-signing work. Both draw their randomness from crypto.getRandomValues, and neither transmits anything.

Work with certificates

CSR Generator
Generate a PKCS#10 certificate signing request and its matching private key in your browser. It supports RSA 2048/4096 and EC P-256/P-384. Nothing is uploaded or transmitted, which matters because the private key never has to leave your machine on its way to a certificate authority.

Cert Decoder
Paste a PEM certificate and read its subject, issuer, validity dates, SANs, key algorithm and SHA-256 fingerprint. Decoding happens in your browser only. It's handy when you're debugging an expired or mismatched cert and just want to see what's inside.

A classic for learning

Text Cipher
Caesar, ROT13, Atbash and Vigenère ciphers, with an adjustable shift, a custom keyword and an instant swap. These are for puzzles, teaching and CTF warm-ups. They are not secure, so don't use them to protect anything real. For that, use the AES tools above.

Why a browser is a reasonable place to do this

No server to trust. Your passphrase, plaintext and private keys stay in the tab.
Standard primitives. The Web Crypto API is built into modern browsers, so these tools use the platform's own cryptography rather than a hand-rolled implementation.
Fast feedback. There's no upload or queue, so generating a key pair or decoding a certificate takes seconds.

Limits worth knowing

Browser-based crypto is convenient, but it's not a substitute for everything:

Your passphrase is the weak point. PBKDF2 at 250,000 iterations slows down guessing, but a short or reused passphrase is still weak. Use a long, unique one.
There's no recovery. If you lose the passphrase for an encrypted file, the file is gone. Authenticated encryption can't be "unlocked" without the key.
Treat generated private keys like any other secret. Store them in a password manager or secrets vault, and think carefully before generating production keys on any machine you don't fully control.
For high-stakes or regulated work, use audited, well-established tooling (for example, OpenSSL, GnuPG or your platform's key management service) and follow your organization's policy.

Try them out

Browse the full Encryption & Keys category. If you spot a bug or want another tool added, such as hashing or JWT utilities, tell us in the comments.

Do you generate keys and CSRs locally, in the browser, or in a managed service? I'd like to hear what your workflow looks like.

28 Free Browser-Based Writing & Editing Tools for Developers and Content Creators

Md Shohan — Sun, 18 Oct 2026 11:37:27 +0000

Developers write more than we admit: READMEs, docs, commit messages, release notes, blog posts, emails to stakeholders. Good writing tools help, but most want an account or upload your draft to a server.

We built the Writing & Editing category on Utility Tools Lab with 28 free tools that run in your browser. Here's a walkthrough of what's inside.

Read and listen to your draft

Text to Speech
Reading a sentence aloud catches what your eyes skip over. Paste your text and the tool reads it back using the voices already installed in your browser, with adjustable rate, pitch and volume and live word highlighting. The browser's own speech synthesis engine does the reading locally, so no audio is generated on a server and nothing is uploaded.

Speech to Text
Dictate into a live transcript with your microphone, using the browser's Web Speech API. It supports 20 languages and has punctuation chips, editing, copy and download.

Improve your style

Style Checker
Highlights passive voice, hedges, -ly adverbs, nominalisations, filler phrases and sentences longer than 25 words in your draft, color-coded and counted.

Passive → Active
Detects passive-voice constructions and rewrites them in active voice when the actor is named. Passives with no actor are flagged with a hint to add the missing subject.

Typo Fixer
Fixes 500+ common English misspellings in one click, with a diff view that strikes through each typo in red and highlights the correction in green.

Capitalization Tool
Seven modes (Title Case, Sentence case, All Words, First Word, Alternating, Inverse and Each Line), with a live preview of all of them at once.

Measure readability

Reading Level
Calculates Flesch Reading Ease, Flesch-Kincaid Grade, Gunning Fog, Coleman-Liau and SMOG scores. Useful for checking whether your docs are readable for a broad audience.

Text Statistics Dashboard
17 metrics at once, including word count, readability, reading time, speaking time, top keywords and character frequency, updating live.

Sentence Counter
Counts sentences, average words per sentence and a Flesch score, and highlights your longest and shortest sentences.

Syllable Counter
Total, per-word and average syllables, with a color-coded word grid and a distribution chart.

Word Counter
Words, characters, sentences, paragraphs, lines and reading time as you type, plus live keyword density.

Analyze keywords and content

Keyword Extractor
Takes a paragraph you've already written and surfaces the single words or 2- and 3-word phrases it repeats most, ranked by frequency and share, with stopword and length filters. Results are ready to copy into a spreadsheet.

Keyword Density and Word Frequency
Rank every word by count and percentage. Word Frequency lets you filter stopwords, set a minimum length, and export to CSV.

Text Similarity
Compare two documents with cosine, Jaccard and character edit-distance scores, plus the words unique to each side and every phrase they share.

Text Summarizer
Truncate text by word or character limit with a custom suffix, or extract the top N sentences by word-frequency relevance.

Score your copy

Headline Analyzer: scores a title on a transparent 100-point rubric covering length, power words, numbers and impact
Subject Analyzer: scores an email subject line on six signals, including urgency, personalisation and spam risk
Copy Scorer: scores landing page copy on readability, sentence length, call to action, customer focus, specificity and clarity
Char Limit Checker: real-time counts for 13 platforms, including Twitter, LinkedIn, Instagram, YouTube, SEO meta and SMS
IG Caption Generator: hook, body, CTA and 25 hashtags, with your choice of tone and niche

Clean and format text

Text Cleaner
Strips HTML tags, emoji, URLs, emails, punctuation, digits and stray whitespace using ten filters you can combine.

Paragraph Formatter
Removes extra spaces, collapses blank lines, trims each line, or joins everything into a single line.

Sentence Splitter
Splits a paragraph into sentences, filters by word count or keyword, and exports as a list, numbered set, JSON array or CSV column.

Column Formatter
Aligns every line to a fixed column width with left, right or center padding, and optional borders, which is handy for code comment blocks and README tables.

Notes and typing

Online Notepad: saves to your browser as you type, keeps up to 20 notes, and downloads any note as Markdown
Standup Notes: Yesterday / Today / Blockers, copied as plain text or Markdown, with a 7-entry history
Avro Bangla Typing: type Bangla on an English keyboard using the Avro Phonetic layout, so ami becomes আমি live

Why client-side

All of these tools work locally in your browser:

Privacy. Drafts, internal docs and unreleased copy never leave your machine.
Speed. There's no upload or queue, so results update as you type.
No friction. No account, no paywall, no email capture.

Try them out

Browse the full Writing & Editing category. If there's a tool you wish existed, or something misbehaves, drop it in the comments.

What's the one editing step you always forget to do before publishing?

25 Free Browser-Based Image & Design Tools (Nothing Gets Uploaded)

Md Shohan — Wed, 14 Oct 2026 10:06:29 +0000

Every developer ends up doing small image jobs: shrinking a hero image, converting a color from the design tool into the notation your CSS uses, checking whether a text color is accessible, or generating a QR code for a demo. Most online tools for these tasks ask you to upload your file to a server first.

We built the Image & Design category on Utility Tools Lab with the opposite approach. It has 25 free tools that run in your browser, with no sign-up. Here's a tour of what's in it and why a few of them work the way they do.

Image optimization

Image Compressor
Compress JPEG, PNG and WebP files, with control over quality and max dimensions. No server upload is involved.

Image Resizer
Resize JPEG, PNG, WebP or GIF files to exact pixels or a percentage. It locks the aspect ratio, steps down smoothly, and re-encodes in your tab.

Format Converter
Re-encode PNG, JPEG, WebP, GIF, AVIF and BMP files into any of four output formats, up to 20 files per run, with a matte color behind transparency.

Image Cropper
Drag-to-select cropping with seven aspect-ratio presets, a rule-of-thirds grid, and adjustable output quality.

Flip & Rotate
Rotate by 90°, 180° or 270°, or flip horizontally and vertically, with an instant preview.

Color and CSS tools

HEX ↔ RGB Converter
Convert between HEX, RGB, RGBA and HSL with a live preview. CSS wants one notation while your design tool hands you another, and this closes that gap.

Contrast Checker
Check WCAG 2.1 contrast ratios between foreground and background colors, with AA/AAA pass/fail results for normal and large text.

Color Palette Generator
Generate palettes from any base color using complementary, triadic, analogous or monochromatic schemes.

Gradient Generator
Build linear, radial and conic CSS gradients visually, with unlimited color stops, angle control and presets. Copy the CSS when you're done.

Color Mixer
Blend two hex colors across 7 linear-RGB midpoints. You can copy individual swatches or export everything as CSS custom properties.

CSS Formatter
Beautify minified CSS with 2-space, 4-space or tab indentation, or minify it to a single line. It preserves string values and data URIs.

Photo effects and editing

Grayscale Converter: grayscale, sepia, high-contrast B&W or inverted colors
Brightness & Contrast: adjust brightness, contrast and saturation, then copy the matching CSS filter or save the full-resolution result
Duotone Generator: two-color duotone with adjustable intensity and blend mode
Image Pixelator: square tiles, scanline bars or halftone dots, with a 2 to 64 px slider
Image Border: solid bands, double rules, Polaroid lips or floating shadows
Watermark Tool: overlay your own text in any corner or tiled across the frame, with opacity and rotation controls
Image Annotator: arrows, shapes, freehand drawing, highlights and text labels on screenshots, with undo/redo and clipboard paste

Utilities worth knowing about

Metadata Viewer
Read the EXIF data hidden in a photo, including camera, lens, shutter speed, ISO, capture date and GPS coordinates. The file is parsed in your browser and never uploaded, which is useful before you share a photo publicly.

QR Code Generator
Generate QR codes from a URL, text, email or phone number and download them as PNG.

SVG Optimizer
Shrink SVG files by stripping editor metadata, rounding path data, shortening colors and dropping unused IDs, with a pixel check that the render is unchanged.

YouTube Thumbnail Grabber
Pull every thumbnail size a video publishes, from 1280x720 down, as JPG or WebP.

Images → PDF and PDF to Images
Combine JPG/PNG files into a single PDF, or export PDF pages as PNG or JPEG at 72, 150 or 300 dpi, rendered client-side with PDF.js.

Wallet QR
Generate a BIP-21 / EIP-681 payment QR for an Ethereum, Bitcoin or Solana address. It auto-detects the chain and supports an optional amount and label.

Design decisions behind the tools

Two choices shaped this category.

One file at a time for heavy operations. A browser will only decode an image so large before the tab gives up. That's why the Image Compressor and Image Resizer each work on a single file rather than a whole folder. Both re-encode through a <canvas> element, so the pixels never leave your machine.

Tools that exist because of a real frustration. The Contrast Checker exists because WCAG 2.1 asks for a 4.5:1 ratio on body text, and nobody can judge that by eye. The HEX to RGB converter exists because the notation your CSS needs often isn't the one your design tool gives you.

Try them out

Browse the full Image & Design category. If a tool is missing or something breaks, tell us in the comments. We read them.

Which image or design task do you find yourself repeating most often?

I Replaced My Productivity Apps with 10 Free Browser Tools (No Sign-Up, No Backend)

Md Shohan — Tue, 13 Oct 2026 15:37:22 +0000

If you're a developer, your day probably looks like this: a standup, a pile of tickets, a few deep-work blocks, and a Slack thread across three time zones. You don't need a heavyweight app for any of it. You need a timer, a scratchpad, and a way to decide what matters.

I went through the Productivity category on Utility Tools Lab, which has 17 free tools. They're client-side, need no account, and most save to your browser. Here's what's worth bookmarking.

1. Stay focused

Pomodoro Timer
25-minute work sessions with short and long breaks, session dots, and a sound alert. Everything is configurable, so you can adjust it if 25 minutes isn't your rhythm.

Focus Timer
For deep work, set a countdown from 1 to 240 minutes in 5-minute steps. It has six presets, a sound alert, and a daily sessions-completed stat. Use it for the long stretches when you're debugging something nasty.

2. Decide what actually matters

Task Prioritizer
This sorts tasks into the Eisenhower Matrix: Do First, Schedule, Delegate, Eliminate. If your backlog feels like everything is urgent, it's a good reality check. Tasks persist in localStorage, so they survive a browser restart.

To-Do List
It has High / Medium / Low priorities, status filters, and a live completion bar. It's simple, and it autosaves.

Goal Tracker
Each goal gets a deadline, a priority, and milestones. Progress is calculated from the milestones you complete, which makes it handy for tracking a side project or learning goal over several weeks.

3. Plan your day

Daily Planner
Build a time-blocked schedule with a progress bar, sorted by time. You can copy it as plain text or download it as Markdown. Plans are saved per date.

4. Build habits

Habit Tracker
It's like a GitHub contribution graph for your habits: an 84-day grid with current and longest streaks and a completion rate. Everything is stored locally.

5. Notes and standups

Online Notepad
A distraction-free notepad that saves as you type. It holds up to 20 notes, shows a live word count, and exports any note as Markdown.

Standup Notes
Fill in Yesterday / Today / Blockers, then copy the result as plain text or Markdown straight into Slack or your team doc. It also keeps your last 7 standups, which helps when you can't remember what you did on Tuesday.

6. Working across time zones

Time Greeting Generator
It generates Good Morning / Afternoon / Evening / Night messages for your device timezone, UTC, or US Eastern, Central, Mountain, or Pacific. It's a small thing, but it saves you from sending "Good morning" to someone who's about to go to bed.

The category also links to a few related tools from elsewhere on the site:

Time Zone Converter: 40 IANA time zones side by side, with DST handled
Date Add / Subtract: includes ISO week number and a copyable ISO 8601 stamp
Countdown Timer: counts down to a date, then switches to elapsed time
Image Annotator: arrows, shapes, and text on screenshots, exported as PNG or JPEG
Speech to Text / Text to Speech: built on the browser's speech APIs

The client-side tradeoff

Running entirely in the browser has clear upsides:

No account or onboarding. Open the page and start working.
No backend to depend on. Your tasks and notes don't live on someone else's server.
Fast. Nothing waits on a network round-trip.

There's one caveat: browser storage is per device and per browser. Clear your site data and your notes and tasks are gone. For anything important, use the Markdown export options on the notepad and planner.

Final thoughts

Productivity doesn't need a subscription. A timer, a prioritized list, and a place for notes cover most of what I need on a normal workday. You can try them all at the Productivity category page.

What's in your lightweight productivity stack? Tell me in the comments. 👇

Top 17 Free Browser Based Productivity Tools

Md Shohan — Mon, 05 Oct 2026 13:04:40 +0000

Most productivity apps want an account, a subscription, and a notification permission before you've done any work. Sometimes you just need a timer, a scratchpad, or a place to dump today's tasks.

Utility Tools Lab has a Productivity category with 17 small tools that run entirely in your browser. There's no sign-up and no server round-trip, and most of them save your data locally. Here are the ones I think are most useful for developers.

Focus and time management

Pomodoro Timer

A Pomodoro timer with the classic 25-minute work sessions, short and long breaks, session dots and a sound alert. Everything is configurable, so you can change the intervals if 25 minutes doesn't suit how you work.

Focus Timer

For longer deep-work blocks, the Focus Timer lets you set a countdown from 1 to 240 minutes in 5-minute steps. It has six quick presets, a sound alert, and a daily sessions-completed stat.

Planning and prioritizing

Task Prioritizer

The Task Prioritizer sorts tasks into the Eisenhower Matrix: Do First, Schedule, Delegate, or Eliminate. It's a good way to tell which tickets are actually urgent and which only feel that way. Tasks persist in localStorage across browser restarts.

To-Do List

The To-Do List has High / Medium / Low priorities, status filters, and a live completion bar. It saves to your browser automatically.

Daily Planner

The Daily Planner builds a time-blocked day plan with a progress bar and sorts entries by time. You can copy the plan as plain text or download it as Markdown. Plans are saved per date, with no account.

Goal Tracker

The Goal Tracker is for longer arcs. Each goal gets a deadline, a priority level, and milestones. Progress is calculated from completed milestones, so you can see at a glance whether a multi-week project is on track.

Habits and notes

Habit Tracker

A GitHub-style 84-day grid, the Habit Tracker shows current and longest streaks, completion rate, and color coding. If you like watching a contribution graph fill up, this applies the same idea to habits. It's saved locally.

Online Notepad

A distraction-free notepad that saves as you type. It keeps up to 20 notes, shows a live word count, and lets you download any note as Markdown.

Standup Notes

The Standup Notes tool has three fields: Yesterday, Today, and Blockers. Copy the result as plain text or Markdown and paste it into Slack or your team channel. It keeps a 7-entry history of past standups, so you can see what you said last week.

Remote work helpers

Time Greeting Generator

Writing to a teammate twelve time zones away, it's easy to get "Good morning" wrong. The Time Greeting generator produces Good Morning / Afternoon / Evening / Night messages from your device's timezone, UTC, or US Eastern, Central, Mountain and Pacific.

Related tools in other categories

The category also surfaces a few handy tools from elsewhere on the site:

Time Zone Converter: converts across 40 IANA time zones at once, with DST handled automatically
Date Add / Subtract: month-end clamping, ISO week number, and a copyable ISO 8601 stamp
Countdown Timer: live countdown to any date, switching to elapsed time once the date passes
Time Card Calculator: worked hours and overtime, with night shift support
Image Annotator: annotate screenshots with arrows, shapes and text, then export as PNG or JPEG
Speech to Text and Text to Speech: built on the browser's Web Speech API and built-in voices

Why client-side matters

Three things make these tools pleasant to use:

No account friction. You open the page and use the tool.
Local persistence. State lives in your browser, so there's nothing to sync and no service to go down.
Small scope. Each tool does one job, which beats a bloated all-in-one app when you just need a timer or a scratchpad.

The tradeoff of browser-local storage is that your data stays on one device and browser. Clear your site data and it's gone, so export anything important (the notepad and planner both support Markdown downloads).

Wrapping up

Small friction, repeated every day, adds up. If you want a no-frills toolkit for focus, planning, and standups, the full Productivity category is worth bookmarking.

What lightweight tools do you use to stay on track? Share them in the comments.

Free Tools Every Competitive Programmer Should Bookmark

Md Shohan — Tue, 08 Sep 2026 03:43:22 +0000

If you've ever lost 20 minutes at 2 AM debugging a submask enumeration loop, or drawn a segment tree on paper for the fifth time this month, this post is for you.

I want to share a collection of 31 free, browser-based tools built specifically for competitive programming — no signup, no installs, code stays client-side. They're grouped at Utility Tools Lab's Competitive Programming category, and they cover almost every "I wish there was a tool for this" moment from contest practice.

Here's a tour of what's inside.

Visualizing structures you normally only imagine

Half the pain in CP isn't the algorithm — it's seeing what your data structure is actually doing.

Graph Visualizer — paste a CP-style edge list and get a force-directed graph you can drag around. Toggle directed/undirected and 0/1-indexing, then copy the adjacency list back out.
Segment Tree Builder — feed in an array, pick sum/min/max/gcd, and watch the tree render, plus grab a full C++ class template.
Sparse Table Builder — visualizes every level of the O(1) RMQ precomputation, with live queries.
Union-Find (DSU) Visualizer — watch path compression and union-by-rank happen live on a forest view.
Path Finder — paint walls on a grid and run BFS to see the shortest path animate, then copy the grid as a C++ 2D vector.
Sieve Visualizer — step through the Sieve of Eratosthenes on a color-coded grid.
Sorting Visualizer and Binary Search Visualizer — step-by-step animations with live comparison counts, or lo/hi/mid tracking on your own array.

These aren't just "nice to look at" — watching the not-found path in binary search, or the moment a submask loop wraps around, is often exactly where off-by-one bugs hide.

Code generators that skip the boilerplate

Some things in CP are conceptually simple but easy to typo under time pressure. These tools generate ready-to-paste C++:

Bitmask Planner — set N ≤ 12, visualize all 2^N states and submask iteration order, get a DP skeleton.
PBDS Generator — Order Statistics Tree boilerplate with configurable key type and comparator.
Matrix Rotation and Matrix Generator — for grid-based problems and test input generation.
Convex Hull — click points on a canvas, get the hull via Andrew's monotone chain, export as a C++ vector.
Math you don't want to hand-compute
Modulo Calculator — modular inverse, fast power mod, nCr mod p with BigInt precision.
Extended GCD — GCD, LCM, Bezout coefficients, full Euclidean trace, BigInt-exact to 10¹⁸.
Combinatorics — nCr, nPr, factorials, Catalan and Stirling numbers with step-by-step working.
Prime Factorizer and MEX Calculator — quick sanity checks mid-contest.
Testing and performance
Stress Tester — paste your brute force, your optimal solution, and a generator; get a downloadable script that hunts for counter-examples.
Offline Judge / Test Runner — run JS solutions against custom test cases in a sandboxed worker and get AC/WA/TLE/RE verdicts.
Big-O Analyzer — benchmarks your algorithm across doubling input sizes and predicts whether it'll TLE.
Complexity Calculator — a reference table plus estimated runtime for any N, from O(1) to O(N!).
The rest of the toolbox

Rounding things out: a Code Formatter for C++/Java/Python, a Bit Visualizer for flipping bits and seeing popcount/clz/ctz live, an Interval Merger for timeline-style overlap problems, and an animated DP Table Builder covering Fibonacci, LCS, 0-1 Knapsack, Coin Change, and Edit Distance with heatmap coloring.

There are also a few adjacent tools tagged into the category that are worth knowing about: a Text Diff Checker (handy for comparing expected vs actual output), a Palindrome Checker, and a standalone Prime Checker.

Why this matters

None of these replace actually understanding the algorithms — but they remove the friction of visualizing what you already know, generating boilerplate you'd otherwise mistype, and verifying your solution before you burn a submission on a TLE or WA. Everything runs client-side in the browser, so there's no setup cost between opening a problem and start debugging.

Full list: utilitytoolslab.com/category/competitiveprogramming

If you try one, the Graph Visualizer and Stress Tester are probably the highest-leverage starting points — one saves you from hand-drawing structures, the other saves you from hunting counter-examples by hand.

Happy grinding. 🏆