.R1 File Extension
File TypeWinRAR Multi-Volume Archive Part 1
This file is saved in a binary format, which requires a specific program to read its contents.
What is an R1 file?
Archive file that is part of a RAR multi-volume archive; contains part one of a compressed volume; stores a compressed part or fragment of a larger file; may use the extensions R0 through R99.
WinRAR creates multi-volume archives and can build them back into the original file.