Choose a ZIP to split
Pick one .zip file. It is read on your device — nothing is uploaded.
Split a ZIP in your browser
This tool takes one large .zip and re-packages its contents into several smaller .zip files, each at or below a target size you pick — 10, 25, 50, 100 MB, or a custom value. It is for getting a big archive under an email attachment limit, an upload cap, or a chat size restriction without any extra software.
Each part is a complete, ordinary .zip that opens on its own in any unzip tool. This is deliberately not a multi-volume or "spanned" archive (the .z01, .z02, .zip set), a format that is fragile and inconsistently supported. Instead the entries are bin-packed across independent archives, and together the parts contain every file from the original.
The reading and re-packaging run in your browser with @zip.js/zip.js. The archive is read on your device and the parts are built locally, so there is no upload and no server round-trip. Filenames keep the UTF-8 flag, so Japanese and other non-ASCII names stay correct on Windows.
Why your archive stays on your device
Privacy here is structural, not a promise. There is no upload step because there is no server to upload to:
- The .zip is read and the parts are built entirely in your browser.
- The page is served as static files and makes no request with your archive data.
- The source is open and anyone can read it (MIT).
- It works offline, which is only possible because nothing leaves the device.
If you want to check for yourself, open your browser's Network panel while you split — no request carries your files. Read the source.
How to use it
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Choose your ZIP
Click to select a .zip file, or drop it anywhere on the page. It is read on your device to list what is inside.
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Pick a target size
Choose 10, 25, 50, or 100 MB, or type a custom size in MB. The plan updates to show how many parts you will get and roughly how big each one is.
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Split and download
Build the parts and download them (part-01.zip, part-02.zip, …). Each one is an independent .zip; open any of them normally, and together they hold every original file.
FAQ
Are the parts a multi-volume / spanned zip (.z01, .z02)?
No. Each part is a normal, self-contained .zip that opens on its own. Multi-volume archives — the .z01, .z02, .zip set that must be kept together and reassembled — are fragile and unevenly supported across tools, so this tool avoids them. It splits the entries across independent archives instead.
Will each part really be under my target size?
Yes. Parts are planned by the uncompressed size of each entry plus the zip's structural overhead, and compression never makes a file larger than that, so every part ends up at or below your target. A well-compressed archive can produce parts that are smaller than the target.
What if one file inside is bigger than the target?
That file goes into its own part, and the plan flags it as larger than the target. A single file cannot be spread across multiple parts without a spanned archive, which this tool intentionally does not create. To get under the limit you would need to shrink or re-encode that file first.
How do I put the archive back together?
You don't need to "join" anything. Because each part is an independent .zip, just extract each part; the files land side by side and you have the full original set. There is no special reassembly step.
Are my files uploaded anywhere?
No. The archive is read and the parts are built entirely in your browser. There is no server component, so your files have no path off your device. The source is open and you can confirm this in your browser's Network panel.
Does it work offline?
Yes. It is a PWA. After the first visit it is cached, so splitting works without a network connection. You can also install it to your home screen.
Is there a size limit?
There is no fixed limit. Because everything runs in your browser, the practical ceiling depends on your device's memory — the archive and the part being built are held in memory. Very large archives may be slower or need more memory.