How to Split a Large File Into Smaller Parts

Sometimes a file is just too big for the pipe you're trying to push it through. An email cap, a USB drive with a size limit, or an old upload form that rejects anything over a certain size. Splitting the file into smaller parts is a classic fix: you break one large file into several chunks, move them, and stitch them back together on the other side.

It's a reliable method that's been around for decades, and it still works. But it's also more fragile than most people expect. If one part goes missing or gets corrupted, the whole file is useless, and your recipient needs the right software to rejoin the pieces.

This guide shows you how to split files on both Windows and Mac, how to reassemble them, what can go wrong, and why a single expiring link is usually the easier path for everyday sharing.

Key takeaways

• 7-Zip (free) splits a file into numbered volumes like .001 and .002; type 25M, 100M, or 4000M for the part size.
• On Mac the built-in split -b 100m command is free; rejoin the pieces with cat part_* > yourfile.zip.
• One missing or corrupted part makes the whole file unusable, because there is no partial recovery.
• A single expiring link (up to 10 files, 200 MB) skips rejoining and needs no software on the recipient's end.

Why Would You Split a File?

Splitting made a lot of sense in the era of floppy disks and email-only sharing. Today the reasons are narrower but still real:

• Email caps. To fit chunks under a 20 to 25 MB attachment limit across several messages.
• FAT32 drives. This older USB format can't hold a single file over 4 GB, so large videos must be split.
• Unreliable connections. Smaller parts are easier to re-download if a transfer drops midway.
• Old upload forms. Some legacy systems reject files above a fixed size.

If none of those apply to you, splitting is probably more hassle than it's worth. There are simpler ways to move a big file, which we'll get to. For the full menu of options, our guide to how to send large files online compares them side by side.

Split a File on Windows

Windows doesn't split files on its own, so you'll use a free archive tool. 7-Zip is the most popular and it's completely free.

Using 7-Zip

1. Download and install 7-Zip from its official site.
2. Right-click your large file and choose 7-Zip > Add to archive.
3. In the dialog, find the Split to volumes, bytes field.
4. Enter a size per part. Type 25M for 25 MB chunks, 100M for 100 MB, or 4000M to fit FAT32 drives.
5. Click OK. 7-Zip creates files named yourfile.zip.001, .002, .003, and so on.

Using WinRAR

WinRAR works almost the same way. Right-click the file, choose Add to archive, and set Split to volumes, size in the dialog. It produces parts named .part1.rar, .part2.rar, and so on. WinRAR is paid software after a trial, so 7-Zip is the better free pick.

Split a File on Mac

Mac users have two good routes: a free app or the built-in Terminal.

Using Keka

Keka is a friendly, low-cost archive app for macOS. Open Keka, set the Split field to your chosen part size (for example 100 MB), then drag your file onto the window. Keka outputs a series of numbered parts you can move or send.

Using Terminal

If you're comfortable with the command line, macOS and Linux include the split command for free:

1. Open Terminal.
2. Type split -b 100m yourfile.zip part_ and press Enter.
3. This creates files named part_aa, part_ab, part_ac, and so on, each 100 MB.
4. To rejoin later, run cat part_* > yourfile.zip.

Terminal splitting is fast and needs no extra software, but the parts have no built-in error checking, so handle them carefully.

Tools at a Glance

How to Reassemble the Parts

Rejoining is where recipients most often get stuck, so send clear instructions along with the files.

Tip: Put the rejoin steps in the same message as the files, and name the exact tool and action (for example, "open the .001 file and choose Extract Here"). A vague "unzip these" is where most recipients stall.

• 7-Zip: Put all parts in the same folder, right-click the .001 file, and choose Extract Here. 7-Zip finds the rest automatically.
• WinRAR: Keep all parts together, double-click the .part1.rar file, and extract.
• Keka: Double-click the first part; Keka reassembles the whole file.
• Terminal: Run cat part_* > yourfile.zip in the folder holding the parts.

The golden rule: every single part must be present and named correctly. Miss one, or let one arrive corrupted, and the file won't rebuild.

Risks and Downsides

Splitting works, but it comes with real trade-offs you should weigh first.

• One missing part breaks everything. No partial recovery; you need all of them.
• The recipient needs matching software. 7-Zip, WinRAR, or Keka, and the know-how to use it.
• More steps means more mistakes. Renamed or reordered parts fail to join.
• No built-in expiry. Parts sit wherever you sent them until manually deleted.
• Corruption risk grows. More files means more chances one gets damaged in transit.

For a folder of documents, compressing first can shrink things enough that you never need to split at all. See how to compress files before sharing for what actually saves space.

Why One Expiring Link Is Usually Simpler

Here's the honest take: for most everyday sharing, splitting is overkill. A single download link solves the same problem with none of the fragility. You upload the file once, share one link, and your recipient clicks to download the whole thing.

With ShareIt.onl you drag in up to 10 files (200 MB total per transfer), pick an expiry from 1 hour to 7 days, and get a link plus a QR code. There's nothing to rejoin, no software for the recipient to install, and the file cleans itself up automatically when the link expires. Compare that to emailing five numbered parts and hoping none get lost.

If your file is bigger than a link tool's cap, then splitting or compressing first makes sense. But for the common case of "this is too big for email," a link is faster for everyone. Our guide on how to email a large file covers exactly how to slot a link into your message.

FAQ