JSON Validator & Lint

JSON validation is the process of checking whether a text string conforms to the JSON specification defined in RFC 8259 and ECMA-404. Valid JSON must use double quotes for strings and keys, separate key-value pairs with colons, separate items with commas (no trailing commas), use matched curly braces for objects and square brackets for arrays, and contain only allowed value types: string, number, boolean, null, object, and array. A validator parses the input and reports any deviations from these rules with specific error locations.

Invalid JSON causes parsing failures that can crash applications, break API integrations, and corrupt data pipelines. A single missing comma or unmatched bracket in a 10,000-line configuration file can take hours to find manually. JSON validators catch these errors instantly with precise error locations. In production environments, validating JSON before processing prevents downstream failures and provides meaningful error messages instead of cryptic parsing exceptions.

The most frequent JSON errors include: trailing commas after the last item in an array or object (remove the comma), single quotes instead of double quotes (replace with double quotes), unquoted keys (add double quotes), comments (JSON does not support comments — remove them or use JSONC), NaN and Infinity values (use null or string representation), and undefined values (use null instead). Each of these errors violates the JSON specification and will cause parsers to reject the data.

Validate JSON at every system boundary — when receiving API requests, reading config files, and processing user input. Use schema validation (JSON Schema) for structural validation beyond basic syntax checking. Implement validation in CI/CD pipelines to catch config errors before deployment. For human-edited JSON files, consider using JSONC (JSON with comments) during editing and stripping comments before validation and deployment.