Paste messy or minified JSON and this free JSON formatter turns it into clean, indented, readable code. It also works as a JSON validator: if something is wrong, such as a missing comma, a trailing comma or single quotes, it tells you the line and column so you can fix it fast. You can minify JSON to save space, sort keys alphabetically, and copy or download the result. It's useful for developers working with APIs, and increasingly for anyone using AI. ChatGPT, Claude and Gemini can return "structured output" as JSON, and a quick check here shows whether the model produced valid JSON before you paste it into your app or spreadsheet. Your data is never uploaded, which matters when it contains API responses or customer details.
Format and validate JSON
Formatted JSON will appear here.
How to use the JSON formatter
- Paste your JSON into the box.
- Click Format to beautify it, or Minify to remove all spaces.
- If there's an error, read the line and column in the message, fix it and try again.
- Copy the result or download it as a .json file.
The most common JSON errors
- Trailing comma after the last item:
[1, 2,] - Single quotes instead of double quotes:
{'a': 1} - Keys without quotes:
{a: 1} - Comments, which standard JSON doesn't allow
- Extra text an AI model added before or after the JSON, such as "Here is your JSON:"
FAQ
Is my JSON uploaded anywhere?
No. It’s parsed by your browser’s built-in JSON engine. Nothing is sent to a server.
What does "minify" do?
It removes all spaces and line breaks, which makes the file smaller for sending over the network. The data stays exactly the same.
How big a file can it handle?
Several megabytes works fine on most computers. Very large files (50 MB+) may be slow in the browser.
Why does my AI-generated JSON fail?
Language models sometimes add a sentence before the JSON, wrap it in ``` code fences, or leave a trailing comma. Remove the extra text, or ask the model to return "only valid JSON".
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