JSON Formatter & Beautifier

A JSON formatter takes JSON text — which is often delivered minified, all on one line — and re-indents it into a readable, hierarchical layout with consistent spacing. It does not change the data, only the whitespace. Along the way a good formatter validates the JSON, so if the text is malformed it tells you exactly where the problem is instead of silently failing. This tool formats, validates, and reports the structure of your JSON in one step, entirely in your browser.

The most common causes are a trailing comma before a closing brace or bracket, using single quotes instead of double quotes, unquoted object keys, and missing or extra commas. JSON is stricter than JavaScript object literals: every key and string must use double quotes, and no trailing commas are allowed. This tool reports the exact line and column of the first error plus a plain-English hint, so you can jump straight to the problem.

JSON technically allows duplicate keys, but virtually every parser keeps only the last value and silently discards the earlier ones. That makes duplicates a dangerous source of data loss and confusing bugs. Standard JSON.parse gives you no warning at all. This formatter detects duplicate keys, shows their path and line number, and reminds you that only the last value survives — a check most online formatters do not perform.

No. All parsing, formatting, validation and analysis happen locally in your browser using JavaScript. Your JSON is never uploaded, logged or stored anywhere. You can even use the tool offline once the page has loaded. That makes it safe for pasting configuration, API responses or other sensitive data — though you should always be cautious with real production secrets in any tool you do not control.

Yes. You can choose 2-space, 4-space, or tab indentation, or switch to Minify to strip all whitespace and produce the most compact valid JSON. The Sort keys option recursively orders every object's keys alphabetically, which is handy for diffing two JSON documents or producing a canonical form. All options re-run instantly as you change them.

After a successful parse the tool reports the size in bytes, the number of object keys, how many objects and arrays the document contains, the maximum nesting depth, and counts of strings, numbers, booleans and nulls. These numbers help you spot surprises quickly — for example unexpectedly deep nesting, a payload far larger than you expected, or a structure that does not match what an API was supposed to return.

Repair makes a best-effort attempt to turn almost-JSON into valid JSON. It removes // line and /* */ block comments, converts single-quoted strings to double-quoted, adds quotes around unquoted object keys, and strips trailing commas before closing braces and brackets. It is string-aware, so it never edits text that appears inside a string value. After repairing, the tool re-validates and lists exactly which kinds of fixes it applied. Some problems — such as a genuine unescaped line break inside a string — cannot be guessed safely, so the tool reports them instead of corrupting your data.

No. The Session History is held only in your browser's memory for the current page view. It is never written to localStorage, cookies or a server, and it is cleared the moment you refresh or close the page. It exists purely so you can quickly jump back to something you formatted a minute ago within the same session. Combined with the fact that all parsing happens locally, nothing about your JSON ever leaves your machine.