Check copied payloads
Catch missing commas, quotes and brackets after copying JSON between tools or documents.
100% local · files never leave your browser
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JSON Syntax Validator
Validate JSON syntax online and get a clear parsing error. The JSON validator runs locally in your browser.
✓ Free to use✓ No signup✓ Runs locally
160 bytes · local only
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Processed entirely in this tab
Your input and result are not sent to JSON Hearth or stored on a server.
When to use it
What Validator helps you do
The syntax validator answers one focused question: can the supplied text be parsed as JSON? It is useful before sending, storing or committing a payload.
Validate configuration
Confirm that a JSON configuration file is syntactically readable before deployment.
Debug API errors
Separate JSON syntax failures from schema, authorization and business-rule errors.
How it works
Validator, without the upload.
Add your data
Paste a value, open a local file or begin with the working sample.
Run the tool
The transformation executes in your browser, not on our servers.
Review the result
Check the output, then copy or download it for your next task.
Important limitations
What to check before using the result
Review required
Syntax validity does not prove that the fields match an API or application contract.
Review required
Use the JSON Schema validator when you need required fields, types or value constraints checked.
Common questions
About Validator
Does JSON Syntax Validator upload my data?
No. Your input is processed by code running in your browser and is not sent to an application server.
Is Validator free to use?
Yes. The tool is free, requires no account and can be used directly in the browser.
Is valid JSON automatically valid for my API?
No. A document can be valid JSON while still containing the wrong fields, types or values for a particular API.
Are comments allowed in JSON?
Standard JSON does not support comments. Formats such as JSONC are separate extensions.