{ }
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Format, validate, and minify JSON with syntax highlighting.
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JSON Validator
Validate JSON against strict syntax rules with line-level errors.
json-validator.tool
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Click Validate - or turn on Live validate - to check your JSON
Nothing you paste here is ever sent to a server - validation happens locally in your browser.
What is a json validator?
A JSON validator checks whether a piece of text is syntactically correct JSON according to the JSON specification (RFC 8259). Beyond a simple pass/fail, a good validator also tells you exactly where the syntax broke - and, once valid, what shape the data actually has: whether the root is an object or array, how many top-level keys or items it contains, and how deeply nested it goes.
How to use this tool
- 1Paste the JSON you want to check into the input box.
- 2Click Validate, or turn on Live validate to check automatically as you type.
- 3If it's invalid, you'll see the exact line and column where parsing failed.
- 4If it's valid, you'll see a quick structural summary - root type, top-level key/item count, max nesting depth, and size in bytes.
Common use cases
Checking a config file or API payload before deploying it
Confirming a hand-written or generated JSON snippet is syntactically correct
Quickly understanding the shape of an unfamiliar JSON response - is it an array or object, how deep does it nest
Catching a stray trailing comma or missing quote before it breaks a build
Good to know
Frequently asked questions
How is this different from the JSON Formatter's Validate button?
They share the same underlying check, but this tool is built specifically around validation - it adds a structural breakdown (root type, key/item count, nesting depth, size) once your JSON is confirmed valid, which the formatter doesn't show.
What does 'Live validate' do?
When turned on, the tool automatically re-validates a moment after you stop typing, instead of requiring you to click Validate each time.
Does it check for duplicate keys?
No - per the JSON specification, parsers are allowed to silently keep the last occurrence of a duplicate key, which is what this tool's underlying parser does. It focuses on syntax validity, not style or convention checks.
Is my data sent anywhere to be validated?
No. Validation runs entirely in your browser using native JavaScript - nothing you paste is transmitted to or stored on a server.
quick_facts.json
{
"runs_in_browser": true,
"data_sent_to_server": false,
"signup_required": false,
"price": "free",
"category": "JSON Tools"
}