Developer Tools
Format, validate, and test code and expressions. 20 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 20 developer tools
JSON Formatter & Validator
Format, validate, and minify JSON with exact line errors, a searchable tree, and private processing.
Code Formatter
Format JavaScript, TypeScript, JSON, HTML or CSS with parser-aware indentation and downloads.
Regex Tester
Test JavaScript regex, inspect capture groups, and preview replacements with a cancellable timeout.
Cron Expression Parser & Builder
Build cron expressions and see their next run times explained.
HTTP Status Codes & Log Analyzer
Look up HTTP status codes and analyze response lines or access logs with counts and explanations.
QR Code Generator
Generate a downloadable QR code from any text or URL.
XML Formatter
Validate and format XML without rewriting attributes, CDATA or meaningful text spacing.
URL Parser
Break a URL into protocol, host, path, and query parameters.
CSS Minifier
Minify CSS while preserving strings, cascade order, custom properties and license notices.
SQL Formatter
SQL beautifier for 20 dialects with keyword case, spaces or tabs, copy and .sql download.
Chmod Calculator
Convert between symbolic and octal Unix file permissions.
JavaScript Keycode Finder
Press any key to see its event.key, event.code and keyCode, plus the modifiers held and auto-repeat.
Mock Data Generator
Generate repeatable test data from a custom schema; export JSON, CSV, NDJSON or SQL.
YAML Formatter & Validator
Format YAML with comments and anchors retained. Validate and download multi-document files.
Barcode Generator
Validate or add GTIN check digits and generate one barcode or a batch label sheet as PNG and SVG.
WebSocket Tester
Test WebSockets with text or binary messages, subprotocols, close diagnostics and log export.
JSON ⇄ XML Converter
Convert JSON and XML locally with explicit arrays, attributes and text while refusing lossy structures.
JSON Diff
Compare JSON by ID, ignore noisy paths and export a strict JSON Patch when the comparison permits.
File Type Checker
Inspect recognized file signatures, extensions and browser MIME without opening or uploading the file.
REST API Tester
Send GET/POST requests and inspect the JSON response and headers.
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.