JSON Validator
Free JSON validator and linter online. Validate JSON syntax in your browser with line-level error messages. No upload, no account, runs locally.
Runs locally in your browser. Your input is not uploaded to DevToolMate servers.
Developer Quick Tips
- Paste JSON and press Ctrl/Cmd+Enter to validate syntax instantly and catch missing commas or unclosed braces.
- Line and column numbers pinpoint exactly where JSON syntax fails so you fix errors fast.
- Common JSON syntax mistakes: missing commas, unquoted keys, extra trailing commas, and unclosed braces.
- Validate JSON syntax before formatting or converting to catch structural problems early.
- Use this JSON linter on API payloads and config files to catch errors upfront.
Frequently asked questions
How do I use a JSON validator online to check syntax?
Paste or type your JSON into the input area and press Ctrl/Cmd+Enter or click Validate. The linter checks syntax instantly in your browser and displays results with line and column numbers if parsing fails. No upload, no server calls.
What is the difference between JSON validator and JSON schema validator?
This tool validates JSON syntax only - it checks if your JSON is well-formed and parseable. JSON schema validation is different: it checks if your data matches a schema contract (required fields, types, patterns). This validator does not validate against JSON Schema, OpenAPI, or custom business rules. Use it to catch syntax errors first, then use a schema validator if you need contract checking.
What JSON syntax errors does this linter catch?
Missing or extra commas, unquoted object keys, truncated files, unclosed braces or brackets, invalid escape sequences, and malformed strings. The validator reports the exact line and column so you locate and fix errors quickly.
Is this JSON validator free and do I need an account?
Yes, completely free with no account required. JSON linting and validation happen locally on your device with no sign-up or login.
Does this JSON linter upload my data to a server?
No. This validator runs entirely in your browser. Your input is never uploaded to DevToolMate servers or any external service. Processing is 100% local and private.
How does JSON formatter relate to this syntax validator?
A JSON formatter beautifies and indents your JSON for readability. This validator checks if your JSON is syntactically correct first. Always validate syntax before formatting - if your JSON has errors, formatters may fail or produce incorrect output.
Will my JSON input be saved after I close the browser tab?
No. Your input stays in memory only while the tab is open. Closing the tab clears it completely. No data is persisted to disk or servers.
Related tools
- JSON Formatter: Online JSON formatter - beautify and format JSON in your browser with adjustable indentation and key sorting. Free, no upload, no account.
- JSON Beautifier: Free JSON beautifier online - pretty print with indentation, sort keys, validate syntax. Runs locally in your browser, no upload, no account.