JSON formatter

Format, validate and minify JSON online. Errors are located to the line and nothing is uploaded: your data stays in your browser.

Free
No sign-up
No file uploaded
Windows, Mac, Android, iPhone

Loading the tool…

About this tool

Paste an API response, a config file or a log: the JSON is indented and validated instantly. If something is wrong, the line and column are shown. Everything runs in your browser, so it is safe for sensitive data.

How to use

Paste your JSON.
Choose the indentation or minify it.
Fix the reported error if any, then copy the result.

Common problems and fixes

“Unexpected token” on a comma

JSON does not allow a comma after the last item of an object or array: remove it.

Single quotes are rejected

Keys and strings must use double quotes ("), not single quotes (').

The JSON contains comments

Standard JSON has no comments: remove // or /* */ lines before validating.

Frequently asked questions

Is my data uploaded?

No. The JSON is parsed by your browser (JSON.parse) and never leaves your device.

What is the difference between format and minify?

Formatting adds line breaks and indentation for reading; minifying removes all whitespace to reduce size.

Why do large numbers change?

JavaScript rounds integers above 2^53 (9,007,199,254,740,991). Send very long IDs as strings.

Is there a size limit?

No, but beyond a few megabytes the display may slow down depending on your device.

Still stuck?

Ask on the forum: the category, the tool, your device sheet and the test result will be filled in for you.