JSON Validator

Instantly validate JSON syntax and structure — detailed error messages with line numbers.

What is JSON Validation?

JSON validation is the process of verifying that a string or file conforms to valid JSON syntax as defined by RFC 7159 and ECMA-404. A valid JSON document must use double-quoted strings, properly nested objects and arrays, correct comma placement, and supported value types (string, number, boolean, null, object, array).

Invalid JSON is one of the most common sources of bugs in API integrations, configuration parsing, and data pipelines. A single missing comma, unescaped quote, or trailing comma can cause an entire application to crash or fail silently. The CodeKent JSON Validator catches these errors immediately, showing you the exact line and character position of any syntax error so you can fix it in seconds.

Beyond basic syntax checking, the validator also provides useful statistics about your JSON structure — the number of keys, nesting depth, array lengths, and data types. This helps you quickly understand unfamiliar JSON payloads from third-party APIs or legacy systems.

Common JSON validation errors include: trailing commas (valid in JavaScript but not in JSON), single-quoted strings (only double quotes are valid in JSON), comments (JSON does not support comments), undefined or NaN values, and improperly escaped characters in strings.

Frequently Asked Questions

What makes JSON invalid?
The most common causes are: trailing commas after the last item, single quotes around strings (must be double quotes), missing quotes around object keys, unescaped control characters, and using JavaScript-specific values like undefined, NaN, or Infinity that don't exist in JSON.
Does JSON allow comments?
No. Standard JSON (RFC 7159) does not support comments. If you need comments in JSON-like config files, consider using JSONC (JSON with Comments), JSON5, or YAML instead.
What's the difference between JSON and JavaScript objects?
JavaScript objects are more permissive — they allow trailing commas, single-quoted strings, unquoted keys, comments, and special values. JSON is a strict subset with tighter rules designed for language-agnostic data interchange.
Can I validate JSON arrays at the root level?
Yes. A valid JSON document can be any JSON value at the root — an object {}, an array [], a string, a number, a boolean, or null. Root-level arrays like [1,2,3] are perfectly valid JSON.

Related JSON Tools

JSON FormatterJSON Tools JSON MinifierJSON Tools JSON Schema GeneratorJSON Tools JSON Path TesterJSON Tools JSON DiffJSON Tools