⚙️ JSON Formatter & Validator

The JSON Formatter & Validator parses any JSON string, tells you immediately whether it's valid, and returns it either nicely indented for reading or minified for smallest byte size. Developers use it constantly: pretty-printing an API response pasted from a curl command, spotting the trailing comma that's breaking a config file, minifying a JSON payload before embedding it in a script tag. Everything runs locally through JavaScript's built-in JSON parser, which means the output is exactly what every other JSON consumer will see.

How to Use This Tool

Paste your JSON into the input box. Press Format to get pretty-printed output with two-space indentation. Press Minify to strip every scrap of unnecessary whitespace for smallest transport size. If the JSON is invalid, the tool reports the position of the parse error so you can find and fix the problem.

What This Tool Checks

Strict JSON: double-quoted keys and string values, no trailing commas, no comments, no single quotes, no unquoted keys, no NaN or Infinity. Anything the browser's JSON.parse rejects, this tool rejects — which is what almost every real JSON consumer does too.

Understanding Your Results

A successful format means the JSON is syntactically valid. It says nothing about whether the data matches a schema you expected — a valid JSON object can still be missing required fields for your application. A parse error message identifies the character position where the parser first got confused; the actual mistake is usually there or a few characters earlier.

How to Fix Common Problems

Common fixes: change single quotes to double quotes; remove trailing commas after the last item in an object or array; quote unquoted keys; strip JavaScript-style comments (JSON doesn't have them); escape backslashes inside string values. If you're editing JSON by hand often, use an editor with JSON syntax highlighting and real-time validation to catch mistakes as you type.

SEO Best Practices

Minify before embedding JSON in HTML or before transmitting over the wire; pretty-print for anything a human will read or diff. When editing JSON config files by hand, keep the file pretty-printed so version-control diffs stay readable. If you need trailing commas, comments, or unquoted keys, use JSON5 or YAML instead — don't try to feed those extensions into a strict JSON parser.

Example

A one-line API response like {"user":{"id":42,"name":"Ada"}} formatted by the tool becomes a three-line indented tree that's much easier to scan. Minifying the pretty version turns it back into the single-line form, byte-identical to the original.

Common Mistakes to Avoid

Don't assume "it looked fine to me" means valid — parsers are strict where humans are forgiving. Don't paste JSON that contains real credentials into any online formatter you don't control (this tool runs entirely in your browser, but many others don't). Don't use JSON.parse on untrusted input in production without try/catch and size limits.