Check If JSON Is Valid Online Free Syntax Checker with Line Number
Validate JSON syntax instantly with exact line and column error positions. Real-time checking. No data sent to server.
Paste JSON to validate
Enable Auto for real-time checking
Free Online JSON Validator with Line and Column Error Detection
Validate any JSON string instantly and catch hidden syntax errors before they break your application. Our tool provides precise line and column numbers for errors, making it easy to fix missing commas, unmatched brackets, invalid quotes, and trailing commas.
Built for developers, API testers, and students who need a quick JSON check without pasting data into external servers. The validator runs 100% in your browser, so your sensitive API payloads, authentication tokens, and data structures remain completely private.
How to Check JSON Validity Without Uploading to Server
- Paste or type your raw JSON into the left editor (or click Load Sample).
- Validation happens automatically if Auto is checked (or press Ctrl + Enter).
- If valid, a green success message appears with JSON structure stats.
- If invalid, a red error shows the exact issue with line and column number.
Find Missing Comma in JSON Online - Key Features
Exact Error Position
When JSON is invalid, the tool calculates and displays the precise line and column number where the syntax error occurs.
Real-Time Validation
With Auto mode enabled, JSON is validated as you type. See the result update instantly with every keystroke.
Structure Stats
When JSON is valid, see the total key count, maximum nesting depth, character count, and line count.
100% Private - No Server
All validation runs locally in your browser using native JavaScript. Your data is never uploaded or transmitted.
JSON Validator - Frequently Asked Questions
Paste your JSON into our validator and it automatically checks syntax in real-time. If invalid, the tool shows the exact error message along with the precise line and column number.
Invalid JSON means the text does not follow strict JSON syntax rules. Common causes include missing commas, extra trailing commas, single quotes instead of double quotes, and unmatched brackets.
No. The validation runs entirely inside your browser using native JavaScript. Your data never leaves your device.
A JSON Validator only checks whether the syntax is correct. A JSON Formatter does the same check but also re-indents the JSON to make it readable.
Yes. Since the validation runs in your browser without server limits, it can handle large JSON payloads. Performance depends on your device.