Free Developer Tools Online
Format, validate, encode and generate — essential utilities for every developer. 23 tools available — all run in your browser, no signup required.
JSON Formatter
Format, beautify and minify JSON with syntax highlighting.
JSON Validator
Validate JSON syntax with detailed error messages and line numbers.
Base64 Encoder/Decoder
Encode and decode Base64 strings and files instantly.
UUID Generator
Generate cryptographically secure UUIDs (v4) in bulk.
Regex Tester
Test and debug regular expressions with live match highlighting.
Color Converter
Convert colors between HEX, RGB, HSL, and HSB formats instantly.
Hash Generator
Generate SHA-1, SHA-256, SHA-512, and MD5 hashes from text.
URL Encoder / Decoder
Encode and decode URL components and query strings.
JWT Decoder
Decode and inspect JWT tokens — header, payload, and expiry.
Password Generator
Generate secure random passwords with custom rules.
Timestamp Converter
Convert Unix timestamps to readable dates and vice versa.
Word Counter
Count words, characters, sentences, and estimate reading time.
Lorem Ipsum Generator
Generate Lorem Ipsum placeholder text for mockups and wireframes.
Cubic Bezier Editor
Interactive cubic-bezier editor with velocity graph, presets, and code export.
Spring Physics Playground
Visualize spring animation physics with stiffness, damping, mass, and velocity controls.
SVG Path Editor
Interactive SVG path editor with draggable anchors, bezier handles, and code export.
Advanced CSS Clamp Generator
Generate fluid CSS clamp() values with a live viewport simulator and responsive graph.
React Render Visualizer
Educational React rendering debugger showing rerenders, prop changes, and memoization.
CSS Grid Visualizer
Interactive CSS Grid playground with drag/drop areas, auto-fit/fill, and minmax visualization.
Flexbox Engine Visualizer
Visual flexbox simulator showing how the browser distributes space with flex-grow, shrink, and basis.
Color System Lab
Professional color engineering tool with OKLCH, LAB, interpolation, WCAG contrast, and palette generation.
Accessibility Toolkit
Color blindness simulator, WCAG contrast analyzer, and semantic HTML accessibility checker.
Frontend Performance Visualizer
Real-time FPS meter, frame budget analysis, RAF timeline, and render pipeline visualizer.
These developer utilities cover the everyday tasks you'd otherwise reach for a CLI or random website to do — formatting JSON, decoding JWTs, generating UUIDs, testing regex. Everything runs client-side with the Web Crypto and standard browser APIs, so you can safely paste tokens and data without it touching a server.
Built for speed and privacy
Pasting an API response, a JWT, or a hash into a random online tool is a real security risk if that tool sends your data to a backend. Every utility here runs entirely in your browser, so secrets and payloads stay on your machine. That also means they work offline once loaded and respond instantly with no network round-trip.
From formatting to visualizing
Beyond the classics — JSON formatter, Base64 encoder, regex tester, hash and UUID generators — the collection includes interactive visualizers for CSS Grid, Flexbox, cubic-bézier easing, and spring physics. They're designed to help you understand and debug front-end behaviour, not just produce output.
Frequently asked questions
Is my data sent to a server?
No. Every developer tool runs entirely in your browser. JSON, tokens, hashes and other input are processed locally and never transmitted — safe for sensitive data.
Do these tools work offline?
Yes. Once a tool page has loaded, the processing happens client-side, so it continues to work without a network connection.
Are the tools free with no signup?
Yes. Every tool is completely free, requires no account, and has no usage limits.