JSON フォーマッター
JSON とデータフォーマット · 無料オンラインツール
JSON のフォーマット、検証、ミニファイ。
Click "Format" to beautify your JSON...整形
乱雑な JSON をお好みのインデントサイズで読みやすく構造化。
ミニファイ
空白を削除して JSON を圧縮 — 本番ペイロードに最適。
検証
JSON が有効かチェックし、位置ヒント付きの明確なエラーメッセージを取得。
JSON フォーマッターの使い方
- 1Paste your input data (JSON, CSV, XML, YAML, etc.) into the input field.
- 2The tool automatically processes and validates your data.
- 3Review the converted output in the result panel.
- 4Copy or download the converted result.
機能と特徴
- ✓完全無料 — 登録不要、サブスクリプションなし、広告なし
- ✓ブラウザ上で完全に動作 — データは端末から送信されません
- ✓高速・軽量 — 即座に結果を表示
- ✓クロスプラットフォーム — デスクトップ・タブレット・モバイル対応
JSON フォーマッターとは？
JSON (JavaScript Object Notation) is a lightweight data-interchange format defined by RFC 8259. It uses human-readable text to represent objects, arrays, and primitive values. A JSON Formatter beautifies minified JSON by adding indentation and line breaks, making it readable for debugging and inspection.
JSON フォーマッターの仕組み
The parser tokenizes the JSON string, validates syntax according to RFC 8259, and builds an in-memory tree. The formatter then serializes the tree back to text with configurable indentation (2 or 4 spaces). Syntax errors are reported with line and column numbers.
よくある使用例
- ✓REST API debugging — inspect request/response payloads
- ✓Configuration files — validate and beautify JSON config
- ✓NoSQL databases — review MongoDB/CouchDB documents
- ✓Log analysis — format JSON log entries for readability
JSON vs XML
JSON is lighter and faster to parse than XML. XML supports attributes and namespaces; JSON only has objects and arrays. JSON maps directly to most programming language data structures, making it the default for modern APIs. XML remains common in enterprise/SOAP environments.
セキュリティとプライバシー
This tool runs entirely in your browser — your JSON data is never uploaded. Be cautious with JSON containing sensitive data (tokens, passwords). JSON itself has no security model; always use HTTPS for transport and validate input on the server.
技術的な詳細
Standard: RFC 8259 / ECMA-404. Data types: string, number, boolean, null, array, object. Numbers are double-precision IEEE 754. Strings must be UTF-8. Keys must be double-quoted strings. Trailing commas are invalid. Comments are NOT supported (use JSONC or JSON5 for comments).
よくある質問
Why does my JSON have a trailing comma error?
RFC 8259 forbids trailing commas. Remove the comma after the last item in objects and arrays.
Can JSON contain comments?
Standard JSON (RFC 8259) does not support comments. Use JSONC or JSON5 if you need comments. Most parsers will reject comments.
What is the maximum JSON size?
The spec sets no limit, but browsers and servers impose practical limits (typically 1-100MB). Very large JSON can cause memory issues; consider streaming parsers for big data.
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