Don's Tools · Developers · JSON Formatter & Validator

JSON formatter & validator

Beautify, minify and validate JSON right in your browser. Nothing is uploaded.

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Works offline: your JSON is parsed and formatted in your browser with nothing uploaded. Validation shows the exact error message when the JSON is malformed.
JSON Formatter and Validator is a free developer tool that beautifies, minifies and validates JSON entirely in your browser, with nothing uploaded. It uses the browser's strict parser to report the exact error when JSON is malformed, supports 2-space, 4-space or tab indentation, can sort object keys alphabetically, and lets you copy or download the result.

Frequently asked questions

Is my JSON uploaded anywhere?

No. It is parsed and formatted entirely in your browser, so even sensitive data stays on your device. It works offline once loaded.

What does it check when validating?

It uses the browser's strict JSON parser, so it flags trailing commas, missing quotes, unbalanced brackets and other errors, and shows the exact message describing the problem.

What is the difference between Beautify and Minify?

Beautify adds indentation and line breaks so the JSON is easy to read, while Minify removes all unnecessary whitespace to make it as small as possible.

Can it sort the keys?

Yes. Turn on Sort keys to order every object's keys alphabetically, which makes large objects easier to scan and compare.

Is there a size limit?

No fixed limit, though very large JSON is processed in your browser and may be slower on an older device.