File Splitter & Joiner
Cut a big file into parts of the size you choose so it fits an email attachment or upload limit. The parts (.001, .002 …) can be joined back into the original file. To confirm the result matches, use the File Hash Calculator; to bundle files, see the ZIP Maker & Extractor.
🔒 Runs in your browser · Your data is never sent to a server
Drag and drop a file here, or pick it with the button.
Parts
Drag and drop the parts here, or pick several with the button. Each pick adds to the list.
Join order
No parts yet.
How to use
- Choose "Split a file" or "Join parts".
- To split, drop the file into the box, set the size and unit of each part, then press "Split".
- Save the parts one at a time with "Save", or use "Download all in order" or "Download all as a ZIP".
- To join, drop all the parts (.001, .002 …) into the box, check the order and that none are missing, then press "Join and download".
Notes
- Splitting cuts only the needed range with Blob.slice, so the whole file is not loaded into memory twice. The limit still depends on your device’s memory, and files over 1 GB may fail.
- More than 1,000 parts triggers a warning, and more than 10,000 is not allowed. Part numbers use 3 digits (.001), growing to 4 digits at 1,000 parts or more.
- Parts named .001 restore the original when joined here. They match the layout used by 7-Zip and HJSplit, but parts from tools that add their own header are not supported.
- When joining, parts are sorted by number, and joining is blocked if numbers are missing, duplicated, or from different files. The restored name is the part name without the number, and you can change it.
- "Download all in order" may ask your browser for permission to download several files. A ZIP holds up to 100 MB in total (stored, not compressed).
Glossary
File splitting
Cutting one large file into chunks (parts) of a fixed size. The data itself is unchanged; joining every part in order gives back the original file.
.001 format
A naming scheme that appends .001, .002 … to the original file name. It follows the same order as 7-Zip split archives, and joining the parts by number restores the file.
FAQ
How do I send a file that is too big for email?
Split it into parts smaller than the attachment limit (for example about 8 MB for a 10 MB limit) and send them in separate emails. The recipient drops the parts into "Join parts" to get the original back. Splitting does not alter the data.
How do I put the split parts back together?
Drop all the parts (.001, .002 …) into "Join parts" and press "Join and download". They are sorted by number automatically, and joining stops if a number is missing. On the command line, copy /b on Windows or cat on macOS and Linux also works.
How large a file can it split?
There is no fixed cap; it depends on your device and browser memory. A warning appears above 1 GB. Only the needed range is cut out, so the file is not loaded twice, but very large files can still fail.
Are the parts compressed or encrypted?
No. The original bytes are simply cut into pieces, with no compression or encryption. To protect the contents, encrypt the file with an encryption tool first, then split it.
What happens if one part is missing when I join?
The tool stops and shows which numbers are missing, and it does the same for duplicates. Joining with a gap would corrupt videos and archives, so make sure you have every part.
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