How to Format and Validate JSON Online

You've got a response body, a config file, or a log line that's valid JSON — technically — but it's all on one line, no indentation, no line breaks, completely unreadable. Or worse: it's broken somewhere and whatever's consuming it just throws Unexpected token with no line number to go on. A JSON formatter fixes both problems at once: it pretty-prints the structure so you can actually read it, and it validates the syntax so you know exactly where it broke.

Why compressed JSON is so hard to debug by eye

JSON doesn't require whitespace, so most APIs and build tools strip it to save bytes. That's great for a network response, terrible for a human staring at 400 characters on one line trying to find a missing comma. Formatting reintroduces the indentation and line breaks that make the nesting — which object contains which array, which key belongs to which value — visible again.

What "validate" actually catches

Not every JSON-looking string is valid JSON. Trailing commas, single quotes instead of double quotes, unquoted keys, and unescaped control characters inside strings are all common enough that they show up constantly in hand-edited config files and copy-pasted API examples. A formatter parses the text with a real JSON parser before it does anything else, so if the parse fails, you get told exactly where — not just "something's wrong somewhere in this file."

How to format and validate JSON

1. Open the JSON Formatter and paste your JSON.
2. It's parsed and re-printed with proper indentation instantly, on your device.
3. If the JSON is invalid, the parser error tells you where parsing failed so you can fix it.
4. Copy the formatted result or download it.

Nothing you paste is uploaded anywhere — parsing and formatting both run in your browser, which matters if what you're debugging is a real API response with real user data in it.

Common situations this saves time in

• Reading a minified API response to find the field you actually need, without counting braces by hand.
• Tracking down a syntax error in a hand-edited .json config file before your build tool fails on it.
• Cleaning up JSON copied from a Slack message or ticket before pasting it into code.
• Comparing two JSON payloads side by side, which is only practical once both are consistently indented.

Where to go from here

If the data needs to move between formats — say an API returns JSON but a downstream system expects XML — use JSON to XMLto convert it, still without anything leaving your browser. And if you're working with an auth token instead of a data payload, the JWT Decoder does the same paste-and-read job for JSON Web Tokens specifically.