Split and join files

How splitting and joining work

1. Under “Split”, choose a file, set the size of each part and press “Start splitting”.
2. Save every part (such as “name.001”) and the manifest (“name.split.json”), and send them all.
3. The recipient opens “Join”, selects all parts and the manifest together, and presses “Check and join”. If the content matches, the original file can be saved.

A part is just a slice of the original file’s bytes in order. It cannot be opened on its own in the original app (this does not cut a video into shorter videos).

Size units

• KB, MB and GB are multiples of 1,000 (1 MB = 1,000,000 bytes); KiB, MiB and GiB are multiples of 1,024 (1 MiB = 1,048,576 bytes).
• Only whole numbers are accepted. Only the last part is shorter.

How the content is checked (SHA-256)

• When splitting, the SHA-256 of each part and of the whole file is calculated and written to the manifest.
• When joining, part numbers come from the file names, and each part’s size and SHA-256 are compared with the manifest. The SHA-256 of the whole file is calculated and compared as well.
• If any part is missing, selected twice, not in the manifest, or has different content (swapped or damaged), nothing is joined. The page shows which part is the problem.
• The SHA-256 of the original file is shown on the page and in the manifest, so you can also check it with other tools such as sha256sum.

Saving

• In desktop Chrome, Edge and similar browsers, “Save all to a folder” writes the parts and the manifest into a folder you choose. Nothing is written if a file with the same name already exists.
• In other browsers, save the files one at a time. Some browsers ask for permission when several files are downloaded in a row.
• Parts and the joined file are saved directly from the original files, so the whole file is never loaded into memory.

Limits

• Files up to 4 GiB (about 4.3 GB), up to 999 parts, and parts of at least 1 KB.
• Checking reads the whole file once, so large files take time. Progress shows the amount actually read.
• Parts without their manifest cannot be joined. Files split by other software are not supported.