JSON Editor
Edit JSON directly in your browser with live syntax validation. Choose your preferred indent style, and see character count, line count, and total key count update in real time.
{
"project": "my-app",
"version": "1.0.0",
"dependencies": {
"react": "^18.0.0",
"typescript": "^5.0.0"
},
"scripts": {
"build": "tsc && vite build",
"dev": "vite"
}
} 使い方
計算式
JSON.parse(input) → validate → JSON.stringify(parsed, null, indent) 計算例
A package.json with 12 keys across 2 nesting levels shows as 'Valid JSON', 280 chars, 18 lines.
JSON Editing Best Practices
When editing JSON configuration files (like tsconfig.json, package.json, .eslintrc.json), keep these rules in mind:
- All strings must use double quotes — single quotes are invalid in JSON.
- No trailing commas — the last item in an array or object must not have a trailing comma.
- No comments — standard JSON does not support
//or/* */comments. - Keys must be strings — unlike JavaScript objects, JSON keys cannot be numbers or symbols.
Use the live validation status to confirm your edits are syntactically correct before saving or deploying.
よくある質問
Is this a real JSON editor?
This is a browser-based JSON editor with live validation and formatting. It processes your JSON entirely in-browser using native APIs, with no server round-trips.
Can I use this to edit large JSON files?
Yes. The editor is limited only by your browser's memory. For files over several MB, ensure your browser tab has sufficient memory available.
What happens when my JSON has errors?
The tool immediately shows a Syntax Error message with the exact position of the error, so you can fix it without guessing.
Can I download the formatted JSON?
Yes. After formatting, click the Download button below the output block to save the formatted JSON as a .json file directly from your browser.