Free tool · Developer utilities
JSON formatter and validator
Paste JSON to validate and pretty-print it as you type. Broken JSON gets an exact error location and a one-click fix.
Runs in your browser. Nothing you paste is uploaded.
About this tool
JSON formatter: how it works
We wrote this because most JSON formatters stop at "Unexpected token". You get a position number and have to find it yourself. Here the error shows the line and column with a caret under the problem, and the formatted output updates on every keystroke once it parses.
A lot of what people paste is not quite JSON: a JavaScript object from a console, a Python dict from a log, a config file with comments. Fix JSON handles those. It removes comments and trailing commas, converts single and smart quotes, quotes bare keys, adds missing commas between values, and turns True, False, None, undefined and NaN into valid JSON. The fixer is plain rules, not AI, so it gives the same result every time and never makes up values.
Everything runs in your browser, which matters when the JSON is an API response with customer data in it. Files of a few megabytes are fine. The tree view loads big arrays 200 items at a time so the page stays responsive. If you are debugging the Ticketdesk API, every endpoint returns JSON you can paste straight in.
What it does
- Validates as you type with line and column of the error
- Fix JSON: trailing commas, quotes, comments, unquoted keys
- Indent with 2 or 4 spaces or tabs, or minify
- Sort keys alphabetically
- Collapsible tree view for large files
- Open and download .json files
Building on Ticketdesk?
Automate tickets, AI agents and inboxes from your own code.
FAQ
JSON formatter: common questions
How do I validate JSON?
Paste it in the input. Valid JSON shows Valid JSON with its size, line count and depth below the editor. Invalid JSON shows the parser error with the line and column, and the line itself with a caret under the problem character.
Can it fix invalid JSON automatically?
Yes, select Fix JSON when the input is invalid. It handles trailing commas, single quotes, curly quotes, // and /* */ comments, unquoted keys, missing commas and Python or JavaScript literals. Missing brackets are not guessed, so check the error if one is left.
Is this an AI JSON formatter?
No. Parsing uses the browser's JSON.parse and the fixer is a small rule-based tokenizer. That keeps it fast, private and predictable. AI is useful for making up sample data, not for repairing data you need to trust.
Does it work with large JSON files?
Yes. Open a file or paste it, and formatting runs without blocking typing. For very large files the tree view is easier to read than the text output, and it renders long arrays in pages. To compare two JSON documents, format both here and paste them into the diff checker.
Is my JSON sent to a server?
No. Validation and formatting happen in your browser and nothing is uploaded. You can turn off your network after the page loads and it still works.
How do I minify JSON?
Choose Minify in the indentation options. Copy the output or download it as data.min.json. Pick 2 spaces, 4 spaces or tabs to pretty-print it again.