JSON Formatter & Validator
PopularPretty-print, validate and minify JSON with clear error positions.
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About JSON Formatter & Validator
JSON Formatter pretty-prints, validates and minifies JSON, and when the JSON is broken it tells you the line and column where parsing failed rather than just refusing.
The error position is the point. Most invalid JSON comes from four things: a trailing comma after the last item, single quotes instead of double, an unquoted key, or a stray control character pasted in from somewhere else. Being told "unexpected token at line 42, column 8" turns a hunt through a thousand lines into a two-second fix.
Sorting keys makes diffs readable. Two JSON files with the same content in a different key order look completely different to a diff tool. Sort both alphabetically and the real changes stand out. It is also the quickest way to compare two API responses that should match.
Escaping non-ASCII rewrites accented characters and emoji as \u sequences. Modern systems handle UTF-8 fine and you rarely need this, but it will save you when a config file is being read by something older that mangles anything outside ASCII.
It formats as you type, with no run button and no round trip to a server. That is worth more than convenience here: JSON pasted into a formatter is very often an API response containing tokens, customer records or internal identifiers. Pasting that into a website hands it over. Nothing typed here leaves the tab.
How to use JSON Formatter & Validator
- Paste your JSON. Type or paste it into the box. It formats as you go — nothing is sent anywhere, which matters when the JSON is an API response full of tokens.
- Read the error, if there is one. Invalid JSON gets the exact line and column where parsing failed. Look first for a trailing comma, single quotes, or an unquoted key.
- Choose pretty or minified. Pretty-print with 2 spaces, 4 spaces or tabs to read it. Minify to strip every unnecessary byte before shipping it.
- Sort keys if you are comparing. Sorting alphabetically makes two versions of the same object directly comparable in a diff tool.
Frequently asked questions
Where exactly is my JSON invalid?
The error message gives the line and column of the first problem, rather than just saying the document is invalid. Trailing commas and single quotes are the two most common causes.
Are my files uploaded when I use JSON Formatter & Validator?
No. JSON Formatter & Validator runs entirely inside your browser. Your text is read locally, processed on your own device, and handed straight back to you. You can confirm this yourself: open your browser's developer tools, watch the Network tab, and run the tool — no request carries your data anywhere.
Is JSON Formatter & Validator free?
Yes, completely. No account, no sign-up, no watermark on your output, and no cap on how many times you can use it. The project is open source under the AGPL licence.
Does JSON Formatter & Validator work offline?
Mostly. The site caches itself after your first visit, so it keeps working without a connection. Tools that need a specialised library — PDF editing, OCR, QR codes, MP3 encoding — need a connection the first time you run them, then that library is cached too.