What's the file size limit?

The API endpoint accepts up to 1 MB of JSON per request. For larger files, run the formatter locally: node -e "console.log(JSON.stringify(JSON.parse(require('fs').readFileSync('input.json','utf8')),null,2))"

Yes — enable the 'Sort keys' option to sort object keys alphabetically at every level of nesting. Array element order is always preserved because arrays are ordered by definition.

Does this verify the signature?

Yes — enter your HMAC secret or RSA/ECDSA public key in the Verify section. For HS* algorithms the secret is a plain text string; for RS*/ES* provide a PEM-formatted public key matching the private key that signed the token.

Is my token sent to a server?

The browser-side decoder never makes a network call — decoding is done entirely in JavaScript. The signature-verification call does send your token and key over HTTPS to a server-side endpoint, but neither is logged or stored.

Tool comparison

JSON Formatter vs JWT Decoder

JSON Formatter (formatting) and JWT Decoder (encoding) come from different categories but appear together in developer workflows. This guide explains what each does and when to reach for one over the other.

Bottom line

JSON Formatter works with any JSON document; JWT Decoder specifically handles the three-part token format and Base64-URL-decodes each segment. A JWT's payload is valid JSON — paste a decoded payload into JSON Formatter to explore nested claims in detail.

What each tool does

JSON Formatter

JSON (JavaScript Object Notation) is a lightweight text format for representing structured data using key-value pairs, arrays, strings, numbers, booleans, and null. It is the dominant data interchange format for REST APIs, configuration files, and data storage. A JSON formatter parses a JSON string and re-serializes it with consistent indentation and line breaks (pretty-print) to make it human-readable, or removes all whitespace (minify) to produce the smallest possible representation for transmission or storage. This tool goes further: it validates syntax and reports the exact line and column of any parse error, optionally sorts all object keys alphabetically for consistent diffs, and can repair common JSON-like inputs that are technically invalid — such as trailing commas, JavaScript-style comments, and single-quoted strings.

Open JSON Formatter →

JWT Decoder

A JSON Web Token (JWT) is a compact, URL-safe string used to securely transmit claims between two parties. It consists of three base64url-encoded segments separated by dots: a header, a payload, and a signature. The header specifies the signing algorithm (such as HS256, RS256, or ES256). The payload contains claims — statements about an entity and additional metadata, such as a user ID (sub), an expiry time (exp), an issuer (iss), and any custom application-defined fields. The signature is computed over the header and payload using a secret or private key, allowing the recipient to verify that the token was issued by a trusted source and has not been modified. JWTs are the standard mechanism for stateless authentication in modern web applications: once issued, they travel with every API request (typically in the Authorization: Bearer header) and can be validated without a database lookup. This tool decodes the header and payload instantly without requiring a key, and can optionally verify the signature using your HMAC secret or RSA/ECDSA public key — all within your browser.

Open JWT Decoder →

Side-by-side comparison

Feature	JSON Formatter	JWT Decoder
Category	formatting	encoding
Primary purpose	Pretty-print or minify JSON — with syntax validation.	Decode and verify JSON Web Tokens — header, payload, claims, and signature.
Inputs	json, mode, indent, sort_keys, repair	token, secret, algorithm
Outputs	output, valid, error, error_line, error_column	header, payload, signature, valid_structure, verified

When to use each

Use JSON Formatter when…

How to pretty-print a JSON API response

Convert a minified or compact JSON API response into human-readable, indented output for inspection.

How to minify JSON for production

Remove all whitespace from a JSON file to reduce its size before embedding it in code, APIs, or config files.

Use JWT Decoder when…

How to decode a JWT in your browser

Instantly inspect the header and payload of any JWT without installing software.

How to inspect an Auth0 JWT token

Read the claims inside an Auth0 access token or ID token to debug permissions and user data.

Frequently asked questions

What's the file size limit?: The API endpoint accepts up to 1 MB of JSON per request. For larger files, run the formatter locally: node -e "console.log(JSON.stringify(JSON.parse(require('fs').readFileSync('input.json','utf8')),null,2))"
Does it sort keys?: Yes — enable the 'Sort keys' option to sort object keys alphabetically at every level of nesting. Array element order is always preserved because arrays are ordered by definition.
Does this verify the signature?: Yes — enter your HMAC secret or RSA/ECDSA public key in the Verify section. For HS* algorithms the secret is a plain text string; for RS*/ES* provide a PEM-formatted public key matching the private key that signed the token.
Is my token sent to a server?: The browser-side decoder never makes a network call — decoding is done entirely in JavaScript. The signature-verification call does send your token and key over HTTPS to a server-side endpoint, but neither is logged or stored.