JSONL Validator
Paste JSON Lines (JSONL or NDJSON) to validate every record independently, pinpoint syntax errors by line number, summarize value types, and export valid records as normalized JSONL or a JSON array. Everything stays in your browser.
Validate JSON Lines data one line at a time, count valid values and errors, summarize detected JSON value types, and export either normalized JSONL or a JSON array.
How to validate JSONL
- Paste JSON Lines text into the input area.
- Choose whether blank lines should be skipped.
- Select normalized JSONL or JSON array as the output format.
- Run validation or wait for the automatic check.
- Review line-numbered errors, then copy or download the valid output.
Line validation and output behavior
The validator splits on CRLF or LF and applies JSON.parse independently to each processed line. Valid lines are reserialized with JSON.stringify, while invalid lines are recorded with their original one-based line number and parser message.
The summary counts objects, arrays, strings, numbers, booleans, and null values. The error panel displays at most the first 20 errors and reports how many additional errors remain. Only successfully parsed values are included in normalized JSONL and array output.
Privacy and limitations
Validation and export preparation happen locally in the browser. JSONL requires each processed line to be independently valid JSON; multi-line JSON objects are therefore not supported. If blank-line skipping is disabled, an empty line is passed to JSON.parse and becomes an error.
Frequently asked questions
Can each line contain a different JSON type?
Yes. Objects, arrays, strings, numbers, booleans, and null are all counted separately when valid.
Are blank lines ignored?
They are ignored by default. Disable Skip blank lines if you want them to be validated and reported as errors.
Does one bad line invalidate all good lines?
No. Valid lines are still collected and can be copied or downloaded.
How many errors are shown?
The interface lists the first 20 and reports the number of additional errors.
Can I turn valid JSONL into one JSON array?
Yes. Choose the array output format to serialize all valid parsed values into a pretty-printed array.