Split a large file into parts — and join them back
cut locally · nothing uploaded
about this tool
The split.tools file splitter cuts any file — a video, a disk image, a database dump, a ZIP that's too big — into numbered parts of a size you choose, and the joiner puts them back together byte for byte. It's the browser equivalent of HJSplit or 7-Zip's “split to volumes”, without installing anything.
Parts follow the universal name.ext.001, .002 … convention and are plain consecutive byte ranges, so they can be rejoined anywhere: in this page, by opening the .001 in 7-Zip, with copy /b on Windows, or with cat on macOS and Linux. Presets cover the limits people actually hit — 25 MB email attachments, GitHub's 100 MB file cap, and FAT32's 4 GB − 1 byte maximum file size on USB sticks.
Splitting costs no memory and no time: each part is a Blob.slice of your file, a reference rather than a copy. The only full read is the optional CRC-32 pass that writes a standard .sfv checksum file, which lets the joiner (or any SFV checker) prove every part arrived intact.
under the blade
- Split by
- Max part size (bytes, MB) or number of equal parts
- Naming
- name.ext.001, .002 … — zero-padded, 7-Zip / HJSplit / WinRAR-compatible
- Format
- Raw byte ranges — no headers or container, so any concatenation tool rejoins them
- Integrity
- Optional .sfv file with a CRC-32 per part; the joiner verifies before joining
- Presets
- 10 MB (Discord), 25 MB (Gmail), 100 MB (GitHub), 700 MB (CD-R), 4,294,967,295 B (FAT32)
- Memory use
- Near zero for splitting and joining — parts are references into the source file
- Saving
- One click saves every part into a folder (Chrome, Edge); other browsers download in sequence
- Privacy
- Nothing is uploaded; works offline once the page has loaded
how it works
- 1 cm
Drop the file
Any type, any size. The file opens instantly because it is read straight from your disk — there is no upload.
- 2 cm
Set the part size or count
Type a size or pick a preset such as 25 MB or FAT32's 4 GB limit, or choose a number of equal parts. Keep the .sfv option on to get checksums.
- 3 cm
Save the parts — join them later
Save every part (and the .sfv) to a folder in one click. To rebuild, drop all parts on the Join tab, or use 7-Zip, copy /b or cat.
frequently asked questions
How do I join .001, .002 files back together?
Open the Join tab and drop all parts at once (plus the .sfv if you have it) — the tool sorts them, checks none are missing, verifies checksums and saves the original file. Without this site: open the .001 file in 7-Zip, run copy /b "f.001" + "f.002" "f" on Windows, or cat f.??? > f on macOS/Linux.
How do I copy a file larger than 4 GB to a FAT32 USB drive?
FAT32 stores file sizes in 32 bits, so no file can exceed 4,294,967,295 bytes. Choose the '4 GB − 1' preset, copy the parts to the stick, and rejoin them on the destination computer. Alternatively, reformat the drive as exFAT, which has no practical limit.
Can I split a file to send it by email?
Yes, but leave headroom: attachments are base64-encoded in transit, which inflates them by about 37%, so a 25 MB limit fits roughly 18 MB of file. For Gmail, choose a part size around 18 MB, or share large files through a cloud link instead.
Can I open one part on its own?
Generally no. Parts are raw byte slices, and most formats need their header (at the start) or index (often at the end) to be readable — so only the joined file opens. If you need independently usable pieces, use a format-aware tool such as the PDF, CSV, audio or video splitters.
What is the .sfv file?
Simple File Verification: a text file listing each part's CRC-32 checksum. If a part is truncated or corrupted in transfer its CRC changes, and the joiner (or any SFV checker like QuickSFV or RapidCRC) flags exactly which part to re-send.
Is there a size limit, and is my file uploaded?
No upload, ever — the file never leaves your device. There is no imposed size limit; parts are references into the original file, so even multi-gigabyte files split instantly. Checksumming reads the whole file once at disk speed.