JSONL validator
Validate JSON Lines locally and locate malformed records by line. Download a diagnostic report and, when every line is accepted, normalized JSONL.
At most 10,000 physical lines and 100,000 characters per line. Up to 1,000,000 input characters, 50,000 values per JSON document and 64 nesting levels. Duplicate keys, negative zero and numbers that cannot safely retain their decimal value are rejected. Quote precision-sensitive numbers as strings. Formatting and object member order may change. Processing stays on your device. Each JSON Pointer is limited to 20,000 characters. Paste text to process locally. Review the result before downloading. Results update as you type. Up to 1,000,000 characters.
Your result
How to use JSONL validator
- Paste one JSON value per physical line.
- Review the invalid-line count and line-numbered diagnostics.
- Correct errors, then download the accepted JSONL and report.
Useful next steps
Check one JSON value per physical line
Paste JSONL or NDJSON with one object, array or scalar per line. Blank lines are invalid. A final newline is allowed and does not create another record. Windows CRLF line endings are accepted.
Find the lines that need attention
The report identifies malformed JSON, duplicate object keys and unsupported numbers using one-based line and column positions. It shows up to 500 diagnostics while counting all invalid lines. Error messages do not include the invalid line or neighboring input.
Export only after every line passes
If any line is invalid, only the report is available. Correct those records and rerun to download normalized JSONL. Parsing is performed one line at a time, but the pasted textarea and output remain in memory. This is a bounded text tool, not a huge-file streaming service.