JSON Validator
RFC 8259In-browser onlyValidate JSON against RFC 8259 with line and column error pointers, fix suggestions, and 1-click auto-repair — 100% in-browser.
How to validate JSON in 3 steps
Pinpoint syntax defects, understand standard RFC violations, and repair payloads with one click.
Paste or upload JSON
Paste or upload your raw JSON payload into the editor.
Inspect line pointers
Inspect real-time syntax validation with exact line numbers, columns, and visual caret pointers.
Auto-repair & export
Click 1-Click Auto-Fix to automatically repair common syntax violations, or export the verified payload.
Built for developers who hate cryptic errors
Visual Caret Pointers
See the exact line, column, and character that triggered the error, eliminating guesswork on huge payloads.
1-Click Auto-Repair
Instantly fix single quotes, missing key quotes, JS comments, and trailing commas without manual editing.
Structure Analytics
Inspect root type, maximum object depth, key count, and exact byte savings between raw and minified text.
Zero Telemetry Privacy
100% in-browser processing. Your proprietary API payloads, credentials, and tokens never touch a network server.
Understanding RFC 8259 vs. JavaScript Object Literals
JSON is derived from JavaScript object literal syntax, but it is a strict subset. Many constructs permitted in modern JavaScript (such as trailing commas, single-quoted strings, unquoted property identifiers, and comments) are invalid in RFC 8259 JSON.
When an API or microservice uses strict parsers (such as standard library parsers in Go, Rust, Java, or Python), any non-compliant syntax causes the entire HTTP request to fail with a 400 Bad Request error. Validating your payloads before deploying or mocking saves hours of debugging time.
{ user: 'Ada', }{"user": "Ada"}RFC 8259 Rules at a Glance
The 5 core rules our engine checks against:
- 1Keys must be double-quoted strings
- 2No trailing commas after items or keys
- 3Strings must use double quotation marks (")
- 4No comments permitted (neither // nor /* */)
- 5Numbers cannot have leading zeros (e.g. 01)
Validation and repair execute in your browser with zero network latency and zero tracking.
Frequently asked questions
Everything you need to know about JSON syntax validation and standards compliance.
Which JSON specification does this validator enforce?
Why are trailing commas rejected by the validator?
Can I include comments in standard JSON?
How does 1-Click Auto-Fix work?
Is my data transmitted to any external server?
Why are single quotes not allowed for strings or keys?
Related tools
More browser-based JSON utilities
Stop reading raw brackets. Start seeing connections.
Paste the same JSON into the graph and see it as connected nodes you can search, fold and export — completely free and in-browser.