What is a JSON formatter?

A JSON formatter (also called a JSON beautifier or pretty-printer) takes compact or unformatted JSON text and re-formats it with consistent indentation and line breaks, making it easy for humans to read and understand the structure. This tool formats JSON with either 2 or 4 spaces of indentation and adds syntax highlighting for keys, strings, numbers, booleans, and null values.

Is my JSON data uploaded to a server?

No. All processing happens entirely in your browser using JavaScript. Your JSON data never leaves your device and is never sent to any server. This makes the tool safe to use with sensitive API responses, configuration files, or private data. It even works offline after the page has loaded.

What is the JWT decoder and how does it work?

A JSON Web Token (JWT) is a compact, URL-safe token consisting of three base64url-encoded segments separated by dots: a header, a payload, and a signature. The decoder splits the token, decodes the header and payload segments using atob(), and displays them as formatted JSON. It also extracts standard claims like exp (expiry), iat (issued at), sub (subject), iss (issuer), and aud (audience). Note that signature verification requires a secret key and is not performed — the tool only decodes.

What JSON formats and root types are supported?

The tool supports any valid JSON text regardless of the root type. JSON roots can be objects ({}), arrays ([]), strings, numbers, booleans (true/false), or null. All of these are valid JSON and are handled correctly. The tree viewer, stats, and all other modes work with any root type. Files can be pasted as text or dropped as .json files.

How do I validate JSON and find errors?

Switch to Validate mode and paste your JSON. If the JSON is valid, a green success banner appears. If there is a syntax error, a red error banner shows the exact error message along with the line number and column where the problem was found. Common errors include missing commas, trailing commas, unquoted keys, mismatched brackets, and invalid escape sequences. The tool extracts error position from the browser's native JSON parser, which gives accurate line and column information.

Free JSON Formatter, Validator & JWT Decoder — Online JSON Toolkit

JSON Toolkit — Format, validate, minify and explore JSON data. Decode JWT tokens, inspect structure, get type stats. Nothing leaves your browser.

No upload Data stays local 100% free

Paste JSON here, drop a .json file,
or try the example →

Drop .json file here

{ } Output will appear here

JSON Formatter, Validator & Minifier — Free Online Toolkit

JSON Formatter & Beautifier

JSON Validator

JWT Decoder

JSON Minifier