What is a .001 file?
Split Archive Part · Archive · Various · n/a
A .001 file is the first piece of a file that was split into numbered parts (.001, .002, .003 and so on) to move or store it in chunks. You rejoin the parts with an archive tool to get the original file back.
What is a .001 file used for?
Large files are sometimes split into equal numbered parts so they fit an upload limit, an email size cap or small media. The .001 is just the first chunk; on its own it is incomplete.
To use it, open the .001 in an archive tool like 7-Zip. As long as every numbered part sits in the same folder, the tool reads them in order and reassembles the original file for you.
You need the complete set. If any part is missing, the file cannot be rebuilt, though some formats can partially recover depending on what was lost.
The parts themselves are just data. Whatever caution the finished file deserves (an installer, a video, an archive) applies once it is rejoined, not to the pieces.
What opens a .001 file?
The .001 format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list.
Windows
- 7-Zip (open the .001)
- WinRAR
macOS
- Keka
- The Unarchiver
Linux
- 7z / p7zip
Web
- Not applicable; download all parts and rejoin
Open a .001 file step by step
- Confirm the file really is a .001. Drop it into the WhatFileType identifier, which reads its signature in your browser without uploading anything.
- On Windows, open it with 7-Zip (open the .001) or WinRAR.
- On Mac, use Keka or The Unarchiver.
- On Linux, try 7z / p7zip.
- Still stuck? Convert the .001 to Rejoin the parts to the original file, which opens more widely.
Why can't I open my .001 file?
Almost always because no installed app understands 001. Install one of the apps above, or convert the file to a format your existing software already reads. If double-clicking opens the wrong program instead of nothing at all, the file association is set to the wrong app rather than the file being broken.
The other possibility is that the file is not really a .001 at all. Drop it into the file identifier to check it by its bytes instead of its name. Nothing is uploaded.
How to convert a .001 file
You can convert a .001 file to Rejoin the parts to the original file using a conversion tool or the export menu of an app that opens it.
001 has no fixed magic number, so there is no signature table on this page. Its bytes alone do not prove the format: identification relies on the extension, the structure of the content and the program that created it. The magic-numbers reference lists the formats that do carry one.
Frequently asked questions
What is a .001 file?
A .001 file is the first piece of a file that was split into numbered parts (.001, .002, .003 and so on) to move or store it in chunks. You rejoin the parts with an archive tool to get the original file back.
How do I open a .001 file?
Put every part (.001, .002, .003 and so on) in one folder, then open the .001 in 7-Zip, Keka or a similar tool. It reassembles the parts back into the original file.
I only have some of the parts. Can I still open it?
Usually no. A split file needs every numbered part to rebuild the original. If one is missing you generally cannot reassemble it, so download the complete set again.
Related formats
Sources
Details on this page were checked against authoritative references. How sources are ranked and what is deliberately left out is set out in the methodology.