Open the file in WinRAR, click the "Repair" button in the toolbar.
WinRAR is the native tool. You can also use free alternatives like 7-Zip. macOS: The Unarchiver or Keka are common choices. kaktotio.rar
If you want to compress files into a RAR archive: Open the file in WinRAR, click the "Repair"
Use WinRAR: Right-click the files > "Add to archive..." > Select "RAR" as the archive format. Open the file in WinRAR
RAR files are compressed archives. To access their contents, you need specialized software.