JSON Validator
Find syntax errors in your JSON instantly and pretty-print valid data.
Validate JSON and Pinpoint Errors
A single misplaced comma or unquoted key can break an entire API integration. This JSON Validator parses your data against the strict JSON specification (RFC 8259) and tells you exactly where it fails, then pretty-prints the result when it is valid.
What gets checked
- Trailing commas after the last item
- Single quotes instead of double quotes
- Unquoted object keys
- Missing or mismatched brackets and braces
- Invalid escape sequences and literals
Valid vs. invalid
Valid JSON uses double-quoted keys and strings, lowercase true/false/null, and no trailing commas. When your input passes, the tool re-serialises it with clean indentation so you can copy a tidy version straight back into your project.
Why JSON validation matters
JSON is the backbone of modern web APIs, configuration files, and data interchange. Unlike JavaScript object literals, JSON is strict: keys must be quoted, strings use double quotes, and trailing commas are forbidden. Validating before you ship avoids hard-to-debug 500 errors and parser exceptions in production.
100% Private & Processed Locally
Every conversion on this page runs entirely inside your browser using JavaScript. Your data is never uploaded to a server, logged, or stored â making this tool safe even for sensitive payloads such as API responses, configuration files, and access tokens.
Because there is no network round-trip, conversions are instant and work even when you are offline. It is free to use with no sign-up, no rate limits, and no ads injected into your output.
Frequently Asked Questions
Common questions about the JSON Validator.