JSONフォーマッター

The JSON Formatter and Validator turns minified, escaped or messy JSON into a clean, indented structure you can actually read, and pinpoints syntax errors with their exact location so you can fix them fast.

It runs your input through a strict JSON parser. If parsing succeeds, the tool re-prints the data with a consistent 2-space indent, which means a clean format is also proof that your JSON is valid. If parsing fails, you get a precise error instead of a vague "something is wrong".

Developers reach for it constantly: inspecting an API response, sanity-checking a config file, cleaning up a webhook payload before saving it, or making a large blob diff-friendly before committing it to version control. Readable JSON makes structure, nesting and missing fields obvious at a glance.

Most "invalid JSON" errors come from a handful of causes: keys or strings wrapped in single quotes instead of double quotes, a trailing comma after the last item, comments (which standard JSON does not allow), unquoted keys copied from a JavaScript object, or smart quotes pasted in from a document. The error position tells you exactly where the parser gave up.

Because the whole thing runs in your browser, your JSON never leaves your device. That matters when the payload contains access tokens, customer records or anything you would not want to paste into a random website that quietly uploads it to a server.

Once formatted, copy the result with one click. If you need the opposite, the JSON Minifier strips all whitespace to produce the smallest possible payload for production.