What does JSON validation check?

It checks that your JSON is syntactically correct, properly quoted keys, no trailing commas, balanced brackets, etc.

Does it check JSON Schema?

This tool checks syntax only. To check field names, types, or required keys, use a JSON Schema validator.

Where does validation run?

Validation runs in your browser with JSON.parse. Our servers are not involved at any point.

Does the validator accept comments or trailing commas?

The validator follows the strict JSON grammar, so comments, trailing commas, single-quoted strings, and unquoted keys are reported as errors. Remove them, or convert JSON5 or JSONC to standard JSON before validating.

JSON Validator

Paste your JSON and instantly know if it's valid. Error messages include the line and column of the problem when the browser reports them. All processing runs in your browser.

Input JSON

Output

FORMAT

INDENT

Tips

Paste JSON in the left pane. Output updates instantly.

Runs entirely in your browser

How it works

Validation feeds your input to JSON.parse. If the parse succeeds, the JSON is syntactically correct and a confirmation appears. If it throws a SyntaxError, the tool shows an error message, with the line and column of the offending character when the browser's engine reports a position, so you can jump straight to the problem (trailing comma, unbalanced bracket, unquoted key, and similar).

Example

A trailing comma after the last property. In Chromium browsers the tool reports:

{"a": 1,}

Invalid JSON: Expected double-quoted property name at line 1, column 9.

Processing runs in your browser

All processing happens inside your browser tab. Our servers are not involved at any point.

Technical specification

JSON syntax is defined in RFC 8259 (IETF, 2017) and ECMA-404. The tool parses with the browser's strict JSON.parse, so comments and trailing commas are errors, and writes the result with JSON.stringify.

Standard: ECMA-404 / RFC 8259
Browser API: Native JSON.parse and JSON.stringify
Indent: 2 or 4 spaces (none when minifying)
Size limit: Browser memory

Related operations

For converting between data formats, try CSV to JSON or the YAML formatter. To decode tokens, use the JWT decoder. For escaping URL data, try URL encode.

Frequently asked questions

What does JSON validation check?: It checks that your JSON is syntactically correct, properly quoted keys, no trailing commas, balanced brackets, etc.
Does it check JSON Schema?: This tool checks syntax only. To check field names, types, or required keys, use a JSON Schema validator.
Where does validation run?: Validation runs in your browser with JSON.parse. Our servers are not involved at any point.
Does the validator accept comments or trailing commas?: The validator follows the strict JSON grammar, so comments, trailing commas, single-quoted strings, and unquoted keys are reported as errors. Remove them, or convert JSON5 or JSONC to standard JSON before validating.

Last reviewed September 30, 2026

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