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JSON Formatter & Validator – Free Online Tool

Quick answer: Format, minify and validate JSON online with clear error messages.

About this tool

Paste JSON to pretty-print it with indentation, compress it to one line, or check whether it is valid. Errors show the exact problem so you can fix broken API responses and config files fast.

How to use the JSON Formatter & Validator

1. Enter your text, choose your file or set the options in the tool above.
2. Click the action button for the result you want.
3. Copy or download the output. Nothing leaves your device.

What is JSON and why format it?

JSON is a text format for sending data between apps, websites and APIs. Raw JSON is often one long line that is hard to read. Formatting adds indentation so you can see the structure, while minifying removes spaces to make the file smaller.

{"name":"Ali","skills":["html","css"],"active":true}

Common JSON errors

• Trailing comma: a comma after the last item is not allowed.
• Single quotes: keys and text must use double quotes.
• Unquoted keys: write "name", not name.
• Comments: JSON does not support // or /* */ comments.
• Special values: undefined and NaN are not valid JSON.

How to use the tool well

Paste your data and press Validate first. If it is valid, press Format to read it or Minify to shorten it before sending it in a request. If it is invalid, the error message points to the problem so you can fix it and try again. Everything runs in your browser, so API responses and config files with private data are not uploaded anywhere. For text clean-up, see the Text Diff Checker to compare two versions of a file.

Why use ToolWorlds?

• Free, with no registration
• Private: runs in your browser
• Works on phones, tablets and desktops

Frequently asked questions

Why is my JSON invalid?

Common causes are trailing commas, single quotes instead of double quotes, and unquoted keys.

Is my JSON uploaded anywhere?

No. Parsing happens entirely in your browser.

Is my data safe?

Yes. Processing happens in your browser. Nothing you enter is sent to our servers.

Is it free?

Yes. It is free, with no sign-up or usage limit.

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