Developer tools that keep your data in your browser
Format and compare JSON, decode JWTs, encode URLs and convert Unix timestamps. Free, fast and without accounts.
Tools
5 tools found
- JSONJSON Formatter & ValidatorPretty-print, minify and validate JSON with exact error locations.
- JSONJSON DiffCompare two JSON documents and list every difference by path.
- AuthJWT DecoderRead a JWT's header, claims and expiry without sending it anywhere.
- EncodingURL Encoder & DecoderPercent-encode or decode text and inspect URL query parameters.
- TimeUnix Timestamp ConverterConvert epoch seconds or milliseconds to UTC/local dates and back.
Why use these tools
Processed on your device
Tools run in JavaScript in your browser. Tokens, JSON and other input are not uploaded or stored by this site.
Instant results
Output updates as you type. No sign-up, no waiting for a server round trip.
Precise feedback
Exact error locations, explicit warnings about precision loss and expiry, and documentation on every page.
Guides
All guides- How to Debug API Responses: A Practical WorkflowA step-by-step workflow for failing API calls: status codes, headers, HTML-instead-of-JSON errors, response diffs, JWTs, timestamps and URL encoding.
- How to Compare Two JSON Files (and What Counts as a Difference)Why text diffs mislead for JSON, how key order, array order, null and type changes should be treated, and how to compare JSON with jq, Node.js and Python.
- URL Encoding Explained with Practical ExamplesHow percent-encoding works, encodeURIComponent vs encodeURI, plus signs vs %20, double encoding and decoding errors, with tested JavaScript, Python and curl examples.
- JWT Decoding vs. Signature VerificationWhy anyone can read a JWT, what decoding does and does not prove, and how servers should actually verify tokens.
- Common JSON Syntax Errors and How to Fix ThemTrailing commas, single quotes, unquoted keys, raw line breaks and other mistakes that make JSON.parse fail, with fixes.
- Unix Timestamps Explained: Seconds, Milliseconds and Time ZonesWhat epoch time is, how to tell seconds from milliseconds, and how to convert timestamps to UTC correctly in common languages.
A note on privacy
Running in the browser means your input stays on your device, but it does not make sensitive data safe to paste anywhere. Read the privacy policy for exactly what this site does and does not collect.