File Splitter
Split a large file into smaller chunks to bypass attachment or upload size limits.
How to use
- Drop or choose a file.
- Pick a chunk size — 25 MB is a common Gmail-friendly default.
- Click Split to create the parts.
- Download parts individually or all at once.
About this tool
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Drop a file, pick a chunk size, and split it into numbered parts you can download one at a time or all at once. The split uses Blob.slice, which hands the browser a view of the original bytes rather than a copy, so even a file of several gigabytes never leaves your device and never has to fit in memory. Parts are named after the original with a zero-padded partNNofMM suffix, so they sort correctly in any file manager and rejoin in order — cat file.part* > file on macOS or Linux, copy /b on Windows. Chunk sizes are counted in binary megabytes of 1,048,576 bytes, so pick a value slightly under whatever limit you are trying to slip past rather than exactly on it.
Frequently asked questions
How do I rejoin the parts?
On macOS / Linux: 'cat file.part01of04 file.part02of04 … > original'. On Windows: 'copy /b file.part01of04+file.part02of04+… original'.
Is the file uploaded?
No. Splitting uses Blob.slice in your browser, so nothing leaves your device — even multi-gigabyte files.
How big a file can I split?
There's no hard cap, but your browser has to keep blob references in memory. Several GB usually works; if a download fails, try a smaller chunk size.
Is the order important?
Yes — parts must be rejoined in order. The filename includes 'partXX of YY' to make the order explicit.
Do the parts open on their own?
No. Each part is a raw slice of bytes, not a valid file of the original type — only the first carries the header a program looks for. They exist to be rejoined, so nothing will read part 3 of a video or a ZIP until the whole set is back together.
Is 25 MB the right chunk size for email?
Pick a little under whatever the service states. Limits are usually quoted in decimal megabytes while chunk sizes here are binary, and the attachment is re-encoded in transit, which adds roughly a third on top — so a chunk sized exactly to the stated limit is the one that gets bounced.
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