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Files with .r21 extension are RAR archive parts. You need all parts to extract data. The .r21 file is the 22nd part of a multi-volume RAR archive. Open the first .rar file in WinRAR to extract files.
If WinRAR still can’t open .r21 files, your version may be outdated. Check if a newer WinRAR version is available. Newer versions support old formats too.
To associate .r21 files with WinRAR, right-click on a .r21 file. Select Open With and choose WinRAR. Check “Always use this app”. Windows will now open .r21 files in WinRAR by default.
A .r21 file extension indicates a compressed archive file type. Specifically, it is the 22nd part of a multi-part RAR archive. WinRAR software splits archives into numbered parts to compress large files. To extract a .r21 file, you need all the archive parts. Open the first .rar file in the latest WinRAR version. It can extract multi-volume archives.
If your system does not recognize .r21 files, install and associate them with WinRAR. Right-click on a .r21 file and choose Open With. Select WinRAR and check the box to always use it for these files. The registry will store this info to automatically open .r21 files in WinRAR.
WinRAR