JSON Formatter & Validator
Pretty-print, minify, and validate JSON instantly
使い方
- 1Paste your JSON
Drop or paste any JSON string into the input box. Even messy, minified JSON works.
- 2Choose format or minify
Pretty-print with 2 or 4 spaces, or collapse to a single line for embedding.
- 3Copy or download
Copy formatted JSON to your clipboard or download it as a .json file.
JSON Formatter & Validator について
Free online JSON formatter, beautifier, and validator. Paste any JSON to instantly pretty-print with 2 or 4-space indentation, minify to a single line, or catch syntax errors. Runs entirely in your browser - your data never leaves your device. 712 Tools の JSON Formatter & Validator はモダンな JavaScript API を使って完全にブラウザ内で動作します - サーバーがあなたのデータを見ることは一切ありません。つまり、即時の結果、完全なプライバシー、アップロード制限なしです。
デバッグ、簡単な確認、あるいは本番のインシデント対応まで - このツールは何度でも無料で使えます。ウォーターマークなし、サインアップなし、ツール内広告なし。
よくある質問
Is my JSON uploaded anywhere?
No. All parsing and formatting happens in your browser using the native JSON parser. Nothing is sent to a server.
What does the validator catch?
Missing commas, unquoted keys, trailing commas, mismatched brackets, and any invalid JSON per the RFC 8259 spec.
Can it handle large files?
Yes, up to your browser's memory limit. Files over ~50 MB may slow down the pretty-printer but validation stays fast.
Does it support JSON5 or JSONC?
Not yet. Only strict JSON (no comments, no trailing commas, keys must be double-quoted) is supported.
続きを読む
The best free physics editor alternatives for 2D game devs in 2026
Every 2D game needs collision shapes, and every paid physics editor charges you for them. Here's what a physics body editor actually does, what to look for in a free one, and how the current free options - desktop and browser - stack up in 2026.
LLM token counting and API cost estimation: a 2026 developer's guide
Tokens aren't words, GPT-4o and Claude count them differently, and a 1M-context prompt can cost $30. Here's how tokens actually work, and how to estimate cost before you ship.
JSON Schema for LLM structured output: the developer's shortcut
OpenAI's structured output and Anthropic's tool use both want JSON Schema. Here's the draft that works everywhere, the fields models care about, and how to write one from an example in 10 seconds.
HTTP status codes that actually matter for API developers in 2026
You know 200 and 500. But the difference between 401 vs 403, 400 vs 422, and 502 vs 503 decides whether your API is professional or amateur. Here's the short list that matters.
JSON to TypeScript: workflows that scale beyond a single sample
A one-shot JSON → interface tool is great for demos and dead for production. Here are the patterns real teams use to keep types in sync with real APIs.
YAML pitfalls: the Norway problem, indentation, and anchors
YAML looks like the friendly config format until it silently converts 'NO' to false. Here are the traps in YAML 1.1, why 1.2 fixes some of them, and when to switch to JSON.
Markdown flavors explained: CommonMark, GFM, MDX, and why your table doesn't render
Markdown looks universal until you paste a GitHub table into a Discord post. Here's what each flavor supports, and how to pick one for your project.
The Unix timestamp cheat sheet every developer wishes they had bookmarked
Seconds vs milliseconds vs microseconds, ISO 8601 vs RFC 3339, timezones, DST, leap seconds - the reference for every 'wait, is this in ms?' moment.
Cron expressions explained (for people who forget them every time)
The five fields, the special characters, and the schedules everyone actually uses. A field guide for anyone who Googles 'cron every 5 minutes' more than once a month.
JWT explained: what actually goes inside that token
Every login flow you touch these days involves JWTs, but 'JSON Web Token' hides a lot. Here's the three-part structure, the security pitfalls, and when not to use them.
The regex cheat sheet every JavaScript developer actually needs
Forget lookbehind edge cases. Here are the 15 patterns you'll use in real code - validation, extraction, replacement - with the JavaScript-specific gotchas.
Why your JSON won't parse (and how to fix it in 30 seconds)
Trailing commas, unquoted keys, single quotes, comments - the five errors that break 90% of hand-written JSON, and how to catch them without a build step.
関連ツール
Regex Tester
Test JavaScript regular expressions with live matches
SQL Formatter
Format SQL queries with proper indentation and keyword capitalization
JSON Diff
Structural diff of two JSON documents - added, removed, changed
User-Agent Parser
Parse any User-Agent string into browser, OS, device, and engine
Word Counter
Count words, characters, sentences, paragraphs, reading time
Case Converter
Convert text to UPPERCASE, lowercase, camelCase, snake_case, kebab-case, and more