What does JSON validation check for?

JSON validation checks for syntax errors like missing brackets, unclosed strings, trailing commas, invalid characters, and structural issues. In strict mode, it also checks for comments and single quotes which are not allowed in standard JSON.

What is strict mode validation?

Strict mode enforces the official JSON specification. It will flag trailing commas, comments (both // and /* */), and single-quoted strings as errors, even if some parsers might accept them.

Why is my JSON invalid?

Common reasons for invalid JSON include: missing or extra commas, unquoted keys, single quotes instead of double quotes, trailing commas after the last item, comments in the data, and improperly escaped characters.

Can I validate large JSON files?

Yes, you can validate JSON files of any size by uploading them. The validator processes the entire file and reports all errors found.

Free Tool

JSON Validator

Free online JSON validator. Check your JSON syntax, find errors with detailed messages, and validate against strict JSON standards.

Validate JSON syntax instantly
Detailed error messages with line numbers
Strict mode validation
Detect trailing commas and comments
Check for single quotes
Maximum depth validation
File upload support
Free and unlimited usage

Drop a JSON file or click to upload

Input JSON

Strict mode (no trailing commas, comments, or single quotes)

Validation results will appear here

How It Works

JSON String

Any text that should be valid JSON - objects, arrays, or primitive values. Can include common mistakes like trailing commas or comments.

OUT

Validation Report

Clear pass/fail status with detailed error messages showing exact line numbers and descriptions of what needs to be fixed.

Paste or Upload JSON

Enter your JSON data directly in the text area or drag and drop a .json file to upload it.

Choose Validation Mode

Enable strict mode to enforce the official JSON spec, or disable it for more lenient parsing.

Validate

Click "Validate JSON" to check your data. The tool instantly parses and analyzes your JSON structure.

Review Results

See validation status with detailed error messages including line numbers and specific issues to fix.

Frequently Asked Questions

What does JSON validation check for?: JSON validation checks for syntax errors like missing brackets, unclosed strings, trailing commas, invalid characters, and structural issues. In strict mode, it also checks for comments and single quotes which are not allowed in standard JSON.
What is strict mode validation?: Strict mode enforces the official JSON specification. It will flag trailing commas, comments (both // and /* */), and single-quoted strings as errors, even if some parsers might accept them.
Why is my JSON invalid?: Common reasons for invalid JSON include: missing or extra commas, unquoted keys, single quotes instead of double quotes, trailing commas after the last item, comments in the data, and improperly escaped characters.
Can I validate large JSON files?: Yes, you can validate JSON files of any size by uploading them. The validator processes the entire file and reports all errors found.