Format, validate and clean up messy JSON in seconds
JSON is the language most apps use to talk to each other, but the JSON you actually get back from an API or copy out of a log is almost never tidy. It arrives as one long, unbroken line with no spacing, or with broken indentation that hides the structure. This free JSON Formatter & Validator fixes that instantly: paste your JSON and it rewrites it into clean, indented, readable text so you can finally see the shape of your data. The same tool also minifies JSON back down to a single compact line for production, and validates it — pinpointing the exact syntax error and its character position when something is broken.
It is built for anyone who touches structured data: front-end and back-end developers debugging API responses, people editing config files like package.json or tsconfig.json, data analysts cleaning up exported records, and students learning how JSON is structured. There is no sign-up, no install and no upload step. Everything runs locally inside your browser using the same JSON engine your browser already ships with, so it is fast, free, and safe to use even on sensitive payloads like tokens or customer data. Your text is also remembered between visits on your own device, so you can come back and pick up where you left off.
How to use it
- Paste your JSON into the box, type it by hand, or tap 📋 Paste to pull it straight from your clipboard.
- Pick your indentation — 2 spaces, 4 spaces or Tab — from the dropdown.
- Tap ✨ Format to beautify it, ➖ Minify to compress it to one line, or ✓ Validate to just check it.
- Read the status line: a green tick means valid JSON; a red message gives the exact error and jumps your cursor to the problem spot.
- Tap ⧉ Copy to grab the result, or 📥 .json to download it as a file. Use ↩ Load sample any time to see a working example.
Beautify vs. minify: which one do you want?
Beautifying (formatting) adds line breaks and indentation so a human can read the data — this is what you want while debugging, reviewing a response, or writing a config file by hand. Minifying does the opposite: it strips every space and newline to make the smallest possible payload. Minified JSON is what you send over the network or store in a database, because fewer characters mean faster transfers and less storage. The two are completely reversible here — format a file to read it, then minify it again before you ship it. Both operations only rearrange whitespace; the actual data, key order and values stay exactly the same.
What the validator catches (and how to read the error)
Strict JSON has rules that trip people up because they look harmless. Keys and all text values must use double quotes, never single quotes. You cannot leave a trailing comma after the last item in an object or array. Comments are not allowed. Values are limited to strings, numbers, true, false, null, objects and arrays — so things like undefined, NaN or a function will fail. When the validator finds a problem it shows you the parser's own message together with a character position, and it highlights that spot in the text box so you do not have to hunt for it. The most common culprits are a missing comma between items, an unclosed bracket or brace, and a stray comma right before a closing } or ].
Your data never leaves your device
This tool does not send your JSON anywhere. There is no server call, no account and no logging — the formatting, minifying and validation all happen on your own machine using JavaScript that runs in the page. That means you can safely paste configuration containing API keys, internal API responses, or personal records without worrying about them being stored or transmitted. The only thing kept is a copy of your last input in your browser's local storage, purely so the box is not empty when you return; clearing the box or your browser data removes it. Because nothing is uploaded, the tool also keeps working even if your connection drops.