As developers, we constantly need small utilities — format some JSON, decode a JWT, generate a UUID, compress a screenshot before uploading. Most of us either Google around, install a random VS Code extension, or paste sensitive data into some sketchy ad-filled site.
Over the past few months, I've been building Dev Hacks — a collection of 100+ free tools that run entirely in the browser. No signup, no data leaving your machine. Here are the 10 I personally reach for the most:

  1. JSON Beautifier & Validator Debugging an API response? Paste the minified JSON and get it formatted and validated in one click. → _JSON Beautifier _

  2. JWT Decoder
    Need to quickly check what's inside a token without verifying the signature? Decode the header and payload instantly.
    → JWT Decoder

  3. UUID Generator
    For database seeds, session tokens, or test fixtures — generate UUIDs in bulk.
    → UUID Generator

  4. Image Compressor
    Screenshots and assets straight from your design tool are huge. Compress them before committing or uploading — your repo and your users will thank you.
    → Image Compressor

  5. Image Converter (PNG/JPG/WebP/AVIF)
    Need to convert a PNG to WebP for better Lighthouse scores? Drag, drop, done.
    → Image Converter

  6. QR Code Generator
    For WiFi sharing pages, app download links, or event check-ins — generate QR codes with custom colors.
    → QR Code Generator

  7. SQL Formatter
    Inherited a 200-line query written on one line? Format it into something readable.
    → SQL Formatter

  8. Markdown to HTML
    Writing docs or email templates? Convert markdown to clean HTML instantly.
    → Markdown to HTML

  9. Word Counter
    Quick sanity check on string lengths before hitting API limits (OpenAI, SMS gateways, tweet length).
    → Word Counter

  10. JSON Minifier
    Going the other way — strip whitespace from JSON before storing it in a config or env variable.
    → JSON Minifier

Why browser-only matters: every tool above runs 100% client-side with JavaScript. Your API keys, tokens, and data never touch a server. That's the whole point — utilities should be fast and private by default.
All 100+ tools are free at devhackes.tech. If there's a tool you wish existed, drop it in the comments — I'm actively adding new ones every week.