🛠 Developer Tools
10 free, fast developer tools that run entirely in your browser. No sign-up, no data ever leaves your device.
Free Online Developer Tools — Fast, Private & Browser-Based
This collection of free online developer tools lets you format, decode, encode, generate and convert data without installing anything or creating an account. Every tool below runs 100% client-side in your web browser, so your code, tokens and text never leave your device. They work on desktop and mobile, load instantly, and are perfect for quick debugging while building APIs, web apps and scripts.
JSON Formatter & Validator
Paste raw or minified JSON to format JSON with readable indentation, minify JSON to a single line, and validate JSON syntax. The validator flags errors like missing commas, trailing commas and unmatched brackets — ideal for debugging API responses and configuration files.
JWT Decoder
The JWT decoder splits a JSON Web Token into its three parts and base64url-decodes the header and payload so you can inspect claims such as sub, exp and iat. It decodes tokens locally and never asks for your secret key, since it does not verify the signature.
Base64 Encoder / Decoder
Convert text to and from Base64 with correct UTF-8 handling, so emoji and non-Latin characters round-trip safely. Use it to encode Base64 for data URLs and tokens, or decode Base64 back to readable text.
UUID Generator
Generate RFC 4122 version 4 UUIDs (universally unique identifiers) in bulk — up to 500 at once — with an optional uppercase toggle. It uses the browser's crypto.randomUUID() when available for cryptographically strong IDs.
Timestamp ↔ Date Converter
Convert a Unix timestamp (seconds or milliseconds) into a human-readable date in local, UTC and ISO formats, or pick a date and time to get the corresponding epoch timestamp. Handy for log analysis and database debugging.
Regex Tester
Write and test regular expressions against any sample text. Matches are highlighted live, with a match count and a list of capture groups. Supports standard flags like g, i and m, and shows clear errors for invalid patterns.
URL Encoder / Decoder
Safely URL-encode or URL-decode strings using encodeURIComponent. Useful when building query strings, encoding spaces and special characters, or decoding percent-encoded URLs.
Hash Generator
Generate cryptographic hashes — SHA-1, SHA-256, SHA-384 and SHA-512 — from any text, all produced locally with the browser's Web Crypto API. Great for verifying data integrity and creating checksums.
Color Picker / HEX ↔ RGB Converter
Pick a colour or type a value to convert between HEX, RGB and HSL formats. A live preview swatch stays in sync, so designers and developers can copy the exact value for CSS in seconds.
QR Code Generator
Turn any text or URL into a scannable QR code. Choose the size and error-correction level, generate instantly in your browser, then right-click the image to save it. Nothing is uploaded to a server.
Looking for more? Try the financial & date calculators or the live coding playground for HTML/CSS/JS, Markdown, SQL and API testing.
Frequently Asked Questions
Are these developer tools free to use?
Yes, all 10 tools are completely free. There is no sign-up, no download and no server-side processing — everything runs right in your browser.
Is my data sent anywhere when I use these tools?
No. Every tool runs 100% client-side, so your JSON, tokens, text and files never leave your device or get stored on a server.
Do these tools work on mobile?
Yes. The tools are responsive and work in any modern mobile or desktop browser, including Chrome, Safari, Firefox and Edge.
What is the difference between the JWT decoder and a JWT verifier?
The decoder reads the header and payload of a JSON Web Token without a secret. A verifier checks the signature using a secret or public key. This tool only decodes, so you never need to paste a secret key.
Which hash algorithms does the Hash Generator support?
It supports SHA-1, SHA-256, SHA-384 and SHA-512 using the browser's Web Crypto API. MD5 is intentionally not included, as it is not available in Web Crypto.
Can I use these tools for production or commercial projects?
Yes. The tools are free to use for personal and commercial work, and results are computed in your browser using standard, well-tested browser APIs.