JSONフォーマッター＆バリデーター
無料のオンラインJSON整形ツールとバリデーターです。乱雑なJSONを整形したり、本番向けにミニファイしたり、行単位で正確なエラーとともに構文を検証できます。ブラウザで実行されます。
Runs in your browserUpdated Apr 20, 2026
JSON Input
Output
よくある質問
›Is my JSON sent to a server?
No. The formatter runs entirely in your browser — your data never leaves your device.
›What's the difference between Beautify and Minify?
Beautify adds whitespace and indentation for readability. Minify removes all unnecessary whitespace to reduce file size for transport.
›Why does Validate report an error?
JSON requires double-quoted keys, no trailing commas, and no comments. The error message shows the line and column to fix.
›Does it support JSON5 or JSONC?
No — strict JSON only (ECMA-404). Comments and trailing commas are common reasons for parse errors.
›How big a JSON can I paste?
Anything your browser can handle in memory — typically tens of megabytes. Very large files are best processed locally with jq or a script.
›Is the JSON formatter free?
Yes — completely free, no signup, no ads.