JSON Validator & Syntax Checker
Instant validation with the exact line and column of every error.
Find the broken byte, fast
The validator checks your JSON as you type and reports the first syntax error with its precise line and column, underlined in the editor. No more counting braces by hand.
Common failures — a trailing comma after the last item, single quotes instead of double, an unescaped newline inside a string — can be fixed automatically with Repair. Everything runs in your browser — your JSON never leaves your device, so it is safe for API keys, customer records, and production payloads.
What makes JSON invalid?
Strict JSON (RFC 8259) requires double-quoted keys and strings, no trailing commas, no comments, and only true, false, null as literals. JavaScript object notation that works in code often fails as JSON — this tool tells you exactly where, and can convert it into valid JSON for you.
Frequently asked questions
- How do I find where my JSON is invalid?
- Paste it in the editor — the first error is underlined and reported with its exact line and column in the status bar.
- Why is JSON with single quotes invalid?
- The JSON specification (RFC 8259) only allows double quotes for keys and strings. Use Repair to convert single-quoted input to valid JSON automatically.
- Are comments allowed in JSON?
- Not in standard JSON. Formats like JSONC allow them, but strict parsers will fail. Repair strips comments and returns clean, valid JSON.