Merge JSON Files Online

Do all JSON files I merge need the same columns?

Ideally yes — the tool stacks rows from all files in order. If schemas differ, missing columns are filled with null values in the output.

How many JSON files can I merge at once?

There is no hard limit. Add as many files as you need. All files are loaded in your browser and combined in the order you add them.

Is the merged JSON output sorted?

Rows appear in file order — all rows from the first file, then the second, and so on. If you need a specific order, run the result through the Sort tool.

Is my data private?

Yes — completely. Your file is never uploaded to any server. Everything runs locally in your browser using WebAssembly — processing happens entirely inside your tab. Once you close the tab, nothing is retained.

What is the maximum file size?

The free limit is 50 MB. For larger files, performance depends on your device's available memory — most modern machines handle 500 MB to 1 GB comfortably.