JSON Validator Pro

Why use this tool?

• JSON.parse keeps the last of two duplicate keys without complaint, so a document can be perfectly valid and quietly wrong. Nothing in the language will warn you.
• "Valid JSON" and "the JSON this endpoint promised" are different questions, and it is almost always the second one being asked.
• A log or an export is one object per line. Pasted into an ordinary validator, that produces one useless error on line 2.
• API responses carry real data and should not be pasted into a stranger's server.

How to use JSON Validator

1. Paste the document. It is checked as you type.
2. For a log or export, switch to JSON Lines mode.
3. Paste a JSON Schema underneath to check structure as well as syntax.
4. Copy the report if you need to hand it to somebody.

Features

• Errors located by line and column with a caret under the character
• Duplicate key detection, which no parser offers
• JSON Schema draft-07 validation: types, required, bounds, patterns, formats, enums and allOf / anyOf / oneOf / not
• JSON Lines and NDJSON, validated line by line
• Depth, object, array and key counts

Tips

• The usual causes of a parse error, in order: a trailing comma before a closing brace, a single quote where JSON needs a double, an unquoted key, and a newline inside a string.
• If a value is coming through as the wrong one, check for duplicate keys before checking anything else.

Frequently asked questions