JSON Validator

This validator checks your document against the JSON standard while you type and pinpoints the first error with its line, column and a caret under the offending character. It also detects duplicate keys, which most parsers silently overwrite, and summarises the structure with counts of keys, objects, arrays and nesting depth.

How to use the JSON Validator

1. Paste the JSON you want to check.
2. Read the green "Valid JSON" message or the red error with its position.
3. Fix the highlighted character and the result updates immediately.
4. Review any duplicate-key warnings and the structure statistics.

Features

• Strict RFC 8259 syntax validation
• Line and column reporting with a caret under the error
• Duplicate key detection with JSON paths such as $.user.id
• Statistics: keys, depth, objects, arrays, strings, numbers
• Clear messages for common mistakes like single quotes and trailing commas

Benefits

• Catch broken config or API payloads before they reach production
• Spot silent data loss caused by duplicate keys
• Works offline in your browser with no upload

Frequently asked questions

Are duplicate keys invalid JSON?

The JSON standard says keys should be unique but parsers are not required to reject duplicates. Most keep only the last value, so the validator warns you instead of failing.

Does it validate against a JSON Schema?

No. It checks syntax and structure only. Schema validation (required fields, types) needs a separate schema validator.

Why is the column number different from my editor?

Columns count characters from 1 on each line, and a tab counts as one character. Editors that expand tabs to several columns may show a larger number.

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