Merge JSONL Files Online



Free online JSONL merger - combine NDJSON files

Convert directly in your browser, with no upload waiting time, and no risk of data leaks.

Simply choose your JSONL files and the tool will merge them into one JSONL file for you!

Choose JSONL Files to Merge

JSONL (NDJSON, LDJSON) Files:
(Max 10 files, 100M total.)
(More than 10 files? Big than 100M total?)
or drag & drop JSONL files here
 





How to Merge JSONL (3 Steps)

  1. Choose your JSONL files. Select two or more .jsonl or .ndjson files.
  2. Merge. The lines of every file are appended in order into one JSONL stream.
  3. Download the merged file. Save the combined .jsonl file for streaming or import.

Online vs App

Same job, two ways — pick the one that fits your file:

OnlineApp
Free✓Trial
No install✓—
No upload✓✓
Large files / batch✗✓
GUI✓✓
CLI—✓

In short: this page is best for a quick, small file. For large files or batch jobs, use the TextMerger desktop app — it also ships a command line for scripts and scheduled runs.

What to Know About JSONL

  • Each file must contain one JSON object per line.
  • Files are concatenated line by line in the order you add them.
  • The result stays valid JSON Lines and can be streamed by most tools.
  • Lines that are not valid JSON are copied unchanged so you can fix them later.

Frequently Asked Questions

Is JSONL the same as JSON?

No. JSONL (also called NDJSON) stores one JSON value per line instead of a single array, which is easier to stream and append.

Can I merge JSON arrays instead?

This tool expects JSON Lines. Convert JSON arrays to JSONL first, or merge the arrays and wrap them yourself.

Is my data uploaded?

No, the merge is local.

Related Tools

Merge text files | Merge LOG files | Split JSONL file | JSON to CSV | JSON to SQL | Offline JSON merger

Need bigger files or batch conversion?

If this service cannot merge your data correctly, or your files are big than 100M, or more than 10 files at a time, you can merge JSONL files locally by this App: Text Merger, for Windows, Linux, and macOS.

Want to stay in the browser? Subscribe (from $5/month) to raise the online limits.

If you have any question or suggestion, please contact us.