JSON Formatter / Validator
Format, beautify, validate, and minify JSON in your browser with clear error messages. Free online JSON formatter — nothing is uploaded.
Format, validate and minify JSON in one place. Paste raw JSON to beautify it with clean indentation, collapse it to a single line, or find out immediately whether it parses — with an error that points at the problem rather than just saying "invalid". It is a developer's tool used dozens of times a day, which is why it runs locally and returns instantly: API responses pasted from a terminal, a config file that will not load, or a one-line blob nobody can read.
How to use JSON Formatter / Validator
- Paste your JSON into the box. The tool reports immediately whether it parses.
- Use "Beautify" to re-emit it with indentation, which makes nested structure and array boundaries visible.
- Use "Minify" to collapse it back to a single line, which is the form an API request or a config loader usually wants.
- Read the error message if validation fails — it names the position, which is what turns "invalid JSON" into something you can fix.
Who it is for
JSON Formatter is for reading or repairing a JSON payload: an API response pasted from a terminal, a config file that will not parse, or a one-line blob that needs indenting before anyone can reason about it. It is a developer tool used dozens of times a day, which is why it runs locally and instantly.
How it works
- The text is parsed and re-emitted with indentation, which makes nested structure visible.
- Validation reports where parsing failed, including the position, which is what turns "invalid JSON" into something fixable.
- Minifying collapses the same document to a single line, which is the form an API or a config loader usually wants.
What it cannot do
- It validates syntax, not schema — valid JSON can still be the wrong shape for your application.
- Very large documents are slow in the page, because everything runs in the browser.
- Comments are not valid JSON, so a commented config will be reported as an error. That is correct behaviour, not a bug.
- Key order may change on reformatting, which matters only if something depends on it.
Frequently asked questions
Why does my JSON fail to validate when it looks fine?
The usual causes are a trailing comma before a closing bracket, single quotes instead of double, a comment, or an unquoted key. JSON allows none of those, even though JavaScript does — which is why a literal pasted from a source file often fails.
Does it validate the structure I need?
No. It validates syntax only. Valid JSON can still be the wrong shape for your application — a missing field or the wrong type passes here and fails downstream.
Can I put comments in my JSON?
Not and keep it valid. Comments are a JavaScript extension, not part of JSON, so a commented config file will be reported as an error. That is correct behaviour rather than a limitation of the tool.
Will formatting change the data?
No, the parsed value is identical. Key order can change, and numbers may be re-emitted in canonical form, which matters only if something downstream depends on the original text rather than the value.
Is there a size limit?
No hard limit, but very large documents are slow because everything runs in the page rather than on a server.
Is my JSON sent anywhere?
No. Parsing and formatting happen in your browser, so a response containing tokens, keys or customer data never leaves your machine.