Developer Tools
Format, validate, and test code and expressions. 19 tools
The small utilities that interrupt real work: formatting a wall of minified JSON, checking a regular expression against real input, working out what a cron expression will actually do, or looking up what a status code means.
The formatters and testers use the browser's own engines — the same JSON parser and the same regular-expression implementation your code will run — so what you see here is what your application will do.
All 19 developer tools
JSON Formatter & Validator
Format, validate, and minify JSON documents.
Code Formatter
Format HTML, CSS, and JavaScript with Prettier.
Regex Tester
Test regular expressions against sample text with live matches.
Cron Expression Parser & Builder
Build cron expressions and see their next run times explained.
HTTP Status Code Reference
Searchable reference of all standard HTTP status codes.
QR Code Generator
Generate a downloadable QR code from any text or URL.
XML Formatter
Pretty-print or minify XML documents.
URL Parser
Break a URL into protocol, host, path, and query parameters.
CSS Minifier
Strip comments and whitespace from CSS to shrink file size.
SQL Formatter
Pretty-print SQL queries with dialect-aware formatting.
Chmod Calculator
Convert between symbolic and octal Unix file permissions.
JavaScript Keycode Finder
Press any key to see its event.key, code, and keyCode.
Mock Data Generator
Generate fake names, emails, and rows as JSON or CSV.
YAML Formatter & Validator
Validate YAML and re-format it with consistent indentation.
Barcode Generator
Generate CODE128, EAN, UPC, and other barcodes as images.
WebSocket Tester
Connect to a WebSocket server, send messages, and log the traffic.
REST API Tester
Send GET/POST requests and inspect the JSON response and headers.
JSON ⇄ XML Converter
Convert JSON to XML and XML back to JSON.
JSON Diff
Compare two JSON documents and highlight what changed.
What to know before you pick one
A formatter is a syntax check in disguise
The fastest way to find out whether a document is valid is to try to format it. Valid input reformats cleanly; broken input fails at the exact character where the structure stopped making sense. That is often more useful than the formatting itself — a misplaced comma or an unclosed bracket in a large file is far quicker to find this way than by reading.
JSON is stricter than it looks
Trailing commas are not allowed. Keys must be double-quoted. Comments do not exist in the specification, even though many editors accept them. Single quotes are not valid. Most files that “look fine but will not parse” fail on one of those four, and a formatter will point at the exact position rather than leaving you to hunt.
Regular expressions differ between languages
A pattern that works in one language can behave differently or fail in another, because lookbehind, named groups, Unicode handling and escaping rules are not universal. The tester here runs the browser’s own engine, which is the JavaScript one. Treat a result as authoritative for the web and as a strong hint everywhere else.
Decoding a token is not verifying it
A JSON Web Token carries its payload in plain, reversible encoding — anyone holding the token can read what is inside it without any key at all. Reading it tells you what it claims; it tells you nothing about whether the signature is valid or the token is still in date. Never treat a decoded payload as proof of anything, and never paste a live production token into any tool you have not verified runs locally.
These run on your machine, which is the point
Developer data is often the most sensitive thing on this site: configuration files with connection strings, payloads with customer records, tokens that are live. The tools here work inside the browser tab, so none of that is transmitted. The handful in this category that call an AI model are the exception and say so on their own pages before you paste anything.