JSON Formatter & Validator

What does a JSON formatter do?

Minified or poorly formatted JSON, often a single unbroken line copied from an API response or a log, is nearly impossible to read by eye. A JSON formatter adds consistent indentation, line breaks, and spacing so the structure of nested objects and arrays becomes visually obvious, while a validator checks the JSON is actually well-formed and points out exactly where it breaks if it is not.

Formatting and validating are really two sides of the same coin, you almost always want to format JSON in order to read it, and you almost always want to validate it before trusting it in code, which is why both live in the same tool here rather than being split across two separate pages.

How to format and validate JSON online

Paste your JSON, or load the sample data to see it in action. Click Format JSON to beautify it with your chosen indent size, or Validate to check it without changing the layout. If something is wrong, the Validate button tells you exactly what went wrong and where, so you can find and fix the error fast instead of scanning line by line. You can also minify the output for production use, or escape HTML characters when embedding JSON inside a web page.

The indent size is adjustable, so you can match whatever convention your team or codebase already uses, whether that's two spaces, four spaces, or something else entirely, and the minify option strips all of that whitespace back out again when you need the most compact version for shipping.

Common use cases

• Debugging an API response by making its structure readable at a glance.
• Validating hand-written or generated JSON before using it in code, catching missing commas or unmatched brackets.
• Minifying JSON to reduce file size before shipping it in a production app.
• Cleaning up JSON copied from a log file, chat message, or documentation for easier reading.
• Checking the size and shape of a payload, array length or object key count, before working with it further.

Tips for best results

If Validate reports an error, check the position it points to carefully, JSON errors are often caused by a trailing comma after the last item in an array or object, which is a valid pattern in JavaScript but not in strict JSON. Comparing your JSON against the sample data can also help spot small formatting differences quickly.

Why use Convert369's JSON Formatter

Pasting JSON that might include API keys or user data into a random web tool is not something to do lightly, this one processes everything locally in your browser, so nothing you paste is ever sent anywhere. It is free, works instantly on documents of any size your browser can handle, and includes both formatting and validation in one place.

A formatter and validator like this one is also a handy sanity check before opening a support ticket or filing a bug report about “broken JSON”, running the response through Validate first often reveals the actual issue, a missing bracket, an extra comma, in seconds rather than requiring back-and-forth with whoever built the API.