Runs locally in your browser
JSON Validator
Check whether JSON is syntactically valid and see the line and column of the first error. Validation stays in your browser.
Paste a payload when you only need a yes or no plus a pointer to the break. This validator does not pretty-print or minify the text.
JSON.parse runs in this tab. Invalid input never leaves the machine to be checked elsewhere.
How to use
- Paste the JSON to test.
- Run validate.
- Read the success state or the first error with line and column.
How it works
A parse success means the string is well-formed JSON. It does not prove a schema, types, or required keys.
When the engine reports a character position, the page maps it to a line and column so you can jump in the editor.
Examples
Trailing comma
A list that ends with a comma fails parse. The pointer lands near the extra comma so you can delete it.
Single quotes
Keys in single quotes are invalid JSON. The validator flags the first quote instead of silently rewriting.
FAQ
Does valid mean the API contract is right?
No. Valid means syntax only. Schema checks are out of scope.
Why is there no formatted output?
This page is a gate. Use the formatter to indent or the minifier to shrink.
Are duplicate keys reported?
JSON.parse keeps the last duplicate key in typical engines. That is still considered parseable.
Is the sample sent away?
No. Validation is local in this tab.
Related tools
- JSON FormatterPretty-print JSON with a chosen indent so API payloads are readable. Formatting runs in your browser and never leaves this tab.
- JSON MinifierMinify JSON by stripping extra whitespace to shrink request payloads. Compression of the text happens locally in this tab.
- JSON to CSVConvert a JSON object or array of objects into CSV for spreadsheets. Nested keys flatten with dots, all inside your browser.
- Base64 EncoderEncode UTF-8 text to Base64 for data URIs, headers, and embeds. Encoding uses the Web APIs in this tab, with no server hop.
- URL DecoderDecode percent-encoded URLs and query strings back to readable text. Invalid sequences are flagged without a network call.