JSON Formatter & Validator
Paste JSON to pretty-print, minify or validate it. Everything runs offline in your browser — your data is never uploaded, logged or stored.
This tool is fully client-side. No JSON leaves your device, so it is safe for config files, API payloads and tokens you would not paste into a server-side validator.
This json formatter pretty-prints, minifies and validates JSON entirely inside your browser tab. Paste a payload and it reformats as you type, reports the exact line and column of the first syntax error, and shows the key count, maximum nesting depth and minified byte size so you can see the shape of the document at a glance.
It is built for the moments when an API response will not parse and you need the answer in seconds: a trailing comma, a smart quote pasted from a document, or an unescaped newline inside a string. Because nothing is uploaded, it is also safe for config files, access tokens and customer payloads that should never be pasted into a server-side validator.
What it does not do: it will not repair broken JSON for you, convert between formats, or validate against a JSON Schema. It checks syntax and shows you precisely where the problem is.
How to Use JSON Formatter & Validator
- Paste your JSON — Drop the raw response or file contents into the input box on the left; formatting starts immediately.
- Choose an indentation — Pick 2 or 4 spaces for readable output, or Minified to strip every byte of whitespace.
- Read the status line — Valid JSON is confirmed in green; an error shows the message plus the exact line and column to fix.
- Check the document stats — Key count, maximum nesting depth and minified size help you spot unexpectedly heavy payloads.
- Copy the result — One click puts the formatted or minified JSON on your clipboard.
Frequently Asked Questions
Is my JSON uploaded anywhere?
No. The tool is a single page of JavaScript that runs in your browser, with no network calls of any kind. You can open it, disconnect from the internet, and it will keep working. That makes it safe for tokens, credentials and customer data.
Why does it say my JSON is invalid when it looks fine?
The three usual culprits are a trailing comma before a closing brace or bracket, curly typographic quotes pasted from a document or chat client instead of straight double quotes, and single quotes around keys or values. JSON permits none of these. The status line gives you the line and column to inspect.
What is the difference between formatting and minifying JSON?
Formatting adds newlines and indentation so a human can read the structure. Minifying removes every optional space and newline to make the payload as small as possible for transport. Both produce exactly the same data; only the whitespace differs.
Can it handle very large JSON files?
It handles files of a few megabytes comfortably, because parsing happens with the browser's native JSON engine. Extremely large documents may make the text area sluggish, since the whole string is held in memory, so for files above roughly ten megabytes a command-line tool is a better fit.
Does it support JSON with comments or trailing commas?
No, and deliberately so. JSONC and JSON5 permit comments and trailing commas, but standard JSON does not, and most parsers you will send the data to are strict. The validator holds you to the strict specification so problems surface here rather than in production.