JSON Formatter & Validator
100% private — runs on your device, never uploaded. Works offline once loaded.
Paste JSON to instantly format it with indentation, minify it to one line, or validate that it is syntactically correct. Everything runs locally in your browser.
What "formatting" actually does
JSON (JavaScript Object Notation) is a text-based data format built from four structural characters — curly braces for objects, square brackets for arrays, colons pairing keys to values, and commas separating entries. Clicking Format parses your text into that structure and re-serializes it with consistent indentation, turning a single unreadable line dumped by an API into a document you can actually scan. Minify does the reverse — it strips every space, tab, and line break, which is exactly the compact form servers send over the wire, since whitespace between tokens carries no meaning in JSON.
Where this shows up in real work
Developers reach for a JSON formatter constantly while debugging: an API response logged to the console is often one 4,000-character line, and pretty-printing it is the fastest way to spot which field is missing or misspelled. It's just as useful for editing configuration files — package.json, tsconfig.json, GeoJSON exports, or a Postman collection — where a single stray comma can silently break the file until something tries to parse it.
- Inspecting webhook payloads from Stripe, GitHub, or Slack
- Cleaning up a config file before committing it
- Shrinking a payload before embedding it in a URL or a minified bundle
- Checking a hand-written JSON file (like a translation file) is valid before deploying
Common syntax mistakes it catches
JSON is stricter than a JavaScript object literal: keys must be double-quoted strings (not single quotes or bare words), a trailing comma after the last item is not allowed, and there is no comment syntax at all. Validation errors point roughly to where parsing failed, which is far faster than scanning a 200-line file by eye for a missing bracket.
One thing formatting can't fix
JSON numbers are parsed as standard floating point, so very large integers — a 64-bit database ID, for example — can lose precision when round-tripped through almost any JSON tool, this one included. If exact large integers matter downstream, keep them as quoted strings in the source data rather than relying on a formatter to preserve every digit.
Frequently asked questions
Is my JSON uploaded?
No — parsing and formatting happen on your device.
Does it handle large JSON?
Yes — because processing is local, there is no server size limit.
Is my JSON sent to a server when I format it?
No. Parsing and formatting run entirely in your browser's JavaScript engine, so the content never leaves your device.
Is there a size limit on the JSON I can paste?
There's no artificial limit imposed by the tool — very large files (several megabytes) just take longer to parse, depending on your browser's available memory.
What does an "Unexpected token" error usually mean?
It's almost always a trailing comma, single quotes used instead of double quotes, an unquoted object key, or a missing closing bracket — check the position the error message points to.
Does it support comments, like JSONC or JSON5?
No — standard JSON has no comment syntax. If your file uses // or /* */ comments, strip them first or validation will fail on them.
What's the actual difference between Format and Minify?
Format adds indentation and line breaks for readability; Minify removes all whitespace to produce the smallest payload for transmission over a network.
Does formatting or minifying change my data?
No — only whitespace changes. Keys, values, and array order are preserved exactly as they were parsed.
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