JSON Validator
Check whether JSON is valid, and get the exact position and likely cause when it is not.
How to use this tool
- Select your file, drag it onto the box above.
- Processing starts automatically — there is nothing to configure.
- Check the result panel, which shows the original size, the final size and the page count.
- Click Download to save it.
Validation uses your browser’s own JSON parser, so the answer matches exactly what your code will do with the same input.
The specification
| Result | Valid or invalid, with position on failure |
|---|---|
| Reports | Type, key count, nesting depth, size |
| Engine | The browser’s native JSON parser |
| Privacy | Nothing leaves your device |
How it works
This tool runs entirely in your browser. There is no server involved, which means nothing you type or upload is transmitted, stored, or logged — and there are no usage limits, because there is nothing for us to ration.
You can confirm it yourself: open your browser's developer tools, select the Network tab, and use the tool. No request is made.
Who uses this
Debugging an API payload, checking a config file before deployment, or confirming that generated JSON is well-formed.
Frequently asked questions
Does this check against a schema?
No. It checks syntax only — whether the text is parseable JSON. Validating structure against a JSON Schema is a different job and needs a schema to validate against.
What is nesting depth?
How many levels of objects and arrays are inside one another. Deeply nested JSON is harder to work with and some parsers impose limits.
Are comments allowed in JSON?
No. The JSON specification has no comments. Formats such as JSONC and JSON5 add them, but standard parsers reject them.
Are my files uploaded to a server?
No. Everything runs inside your browser on your own device. Your file is never transmitted and never stored by us. You can confirm this by opening your browser’s Network tab while you use the tool — you will see no upload request.
Is there a limit on how many files I can process?
No. There is no daily cap, no account, and no watermark. Because the work happens on your device rather than our servers, there is nothing for us to ration.
Is this tool really free?
Yes — no account, no trial, no watermark, and no cap on usage. It runs on your own device rather than our servers, so there is no cost for us to pass on.
Does it work on mobile?
Yes. The interface adapts to phone and tablet screens, and everything runs in the browser, so there is no app to install.
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Your files stay on your device. This tool runs entirely in your browser. No file is uploaded, transmitted, or stored. You can verify this by opening your browser's Network tab while using the tool.
Disclaimer. Specifications published by exam boards, governments and platforms change without notice. We verify and date every specification on this site, but you should always confirm against the official source before submitting an application. See our full disclaimer.