File Splitter

File Splitter cuts one big file into a numbered series of smaller ones. Drop in a video, a disk image, a database dump, a log file, or anything else, choose how big each piece should be, and the tool lays out the parts as name.part001, name.part002, name.part003, and so on. Each part has its own Download button, and a single button bundles every part into one ZIP if you would rather save a single file.

The usual reason to split a file is a size limit. An email provider caps attachments at 20 or 25 MB, a messaging app or a forum refuses anything above a few hundred megabytes, an old FAT32 USB stick cannot hold a file of 4 GB or more, and a flaky connection makes a single 3 GB upload more likely to fail than six uploads of 500 MB. Cutting the file into parts below the limit gets around all of those, and because every part is a plain slice of the original bytes, putting them back together restores the file exactly.

You choose the split in one of two ways. Chunk size takes a number of megabytes and makes parts of exactly that size, with a shorter last part holding the remainder. A 1 MB chunk here means 1,048,576 bytes, the same unit most operating systems show. Number of parts takes a count instead and divides the file as evenly as possible, so a file split into four parts has four parts whose sizes differ by at most one byte. The tool stops at 999 parts, because the part number is padded to three digits so that the names sort correctly in any file manager, and it tells you plainly when a chunk size would need more parts than that or when the file is already smaller than one chunk.

Splitting does not read the whole file. The browser's file.slice call returns a view onto a byte range of the file on your disk without copying it into memory, so a 20 GB file can be planned and split instantly, and a part is only read when you click its Download button. The ZIP option is the one exception, because the ZIP library has to hold the parts in memory while it builds the archive, so bundling is limited to 1 GB. Above that, use the per-part downloads. The parts are stored in the ZIP without compression, since splitting is about moving bytes rather than shrinking them and most large files are already compressed.

Beside the list of parts the tool writes a plain-text manifest. It records the original file name and exact size in bytes, the number of parts, every part's name, size, and byte range in the order they must be joined, and the commands to rebuild the file. On macOS and Linux that is a cat command over the part files, and on Windows it is copy /b in Command Prompt. The last line states the exact size the joined file must have, which is the quickest way to notice a missing or truncated part. The manifest can be copied, saved as a text file, and is included in the ZIP.

Nothing about this tool involves a server. Your file is never uploaded, the slicing and ZIP creation run in your tab, and no request carries the file name or any of its bytes. That matters for exactly the files people split most often, such as private backups, recordings, and work documents.