JSONL Formatter and Validator
Use JSONL Formatter and Validator, review the result, and keep the original until the output is checked.
Keep your original file until you have checked the downloaded result. Browser memory and format support vary by device.
JSONL contains one JSON value per non-empty line. Invalid lines are reported before download.
How to use JSONL Formatter and Validator
- Paste a .jsonl or .ndjson file into the box, or press Open and choose it from disk.
- Tick Pretty-print each JSON value to see one object over several lines, and Sort object keys alphabetically when you want files to compare cleanly.
- Press Format JSONL; any line that is not a valid JSON value is reported by number before anything is offered for download.
- Fix the reported lines and run it again, then Download formatted.jsonl.
What JSONL Formatter and Validator actually does to your file
Records are parsed one per non-empty line, so blank lines are ignored and a document where a single object spans several lines will not read correctly. The on-screen preview and the downloaded file are deliberately different shapes: the preview is expanded for reading, while the download is one compact record per line, which is the form an ingest pipeline expects. There is no copy button, so take the file. Everything happens in this tab and the input is never sent anywhere.
JSONL Formatter and Validator FAQ
What does JSONL Formatter and Validator do?
Validate JSONL or NDJSON line by line, format valid records, and download the result.
Which files work with JSONL Formatter and Validator?
This category commonly supports JSON, YAML, XML, and CSV. Use the accepted file types shown in the uploader, because support varies by browser and by the engine behind each tool.
Can formatting corrupt my data?
It can if the input was not what the format expects. Long numbers, dates and near-miss syntax are the common cases where a reformatted file no longer matches the original values.
Will my original file be changed?
No. You paste text or open a file to read it, the result appears in the other pane, and only what you copy or download leaves the page.
How is my file processed?
It is not uploaded. The processing is done locally by the parser bundled with this page, so the practical ceiling is your device's memory and the limit shown beside the uploader - no queue, no account, no copy on a server.
What is JSONL?
JSONL stores one complete JSON value on each line. NDJSON is a commonly used name for the same line-oriented format.