JSON validation
Tools and guides for verifying JSON conforms to the spec.
Tools
Validate, lint and format JSON in your browser.
Strict RFC 8259 conformance check.
Warnings for trailing commas, duplicate keys, comments.
Repair JSON with a catalog of common errors.
Compare two JSON documents structurally.
Validate JSON data against a JSON Schema — powered by Ajv.
Guides
The mistakes that cause 90% of parse failures.
JS, Python, Bash recipes.
Causes, positions, and fixes for this common error.
Five root causes — empty string, BOM, HTML response, undefined.
What parsers do and how to find and remove duplicates.
HTML returned instead of JSON — how to detect and fix it.
Truncated JSON — the four root causes and fixes.
json.loads() error causes and fixes with code examples.
Syntax rules, nesting, accessing elements, and common mistakes.
Types, required fields, patterns, $ref, and Ajv validation examples.