Switch -OI[-][:<minsize>] - save identical files as references


Switch -OI[-][:<minsize>] - save identical files as references

If this switch is specified, WinRAR analyzes the file contents before starting archiving. If several identical files are found, the first file in the set is saved as usual file and all following files are saved as references to this first file. It allows to reduce the archive size, but applies some restrictions to resulting archive. You must not delete or rename the first identical file in archive after the archive was created, because it will make extraction of following files using it as a reference impossible. If you modify the first file, following files will also have the modified contents after extracting. Extraction command must involve the first file to create following files successfully.

It is recommended to use -oi only if you compress a lot of identical files, will not modify an archive later and will extract an archive entirely, without necessity to unpack or skip individual files. If all identical files are small enough to fit into compression dictionary specified with -md<n> switch, -s can provide more flexible solution than -oi.

Optional <minsize> value allows to define the minimum file size threshold. Files smaller than <minsize> are not analyzed and not considered as identical. If this parameter is not present, it is assumed to be 64 KB by default. Selecting too small <minsize> may increase the time required to detect identical files.

Supported for RAR 5.0 archives only.

Use -oi- if you wish to disable identical file processing enabled in WinRAR configuration.

This switch is the command line equivalent of Save identical files as references option in "Archive name and parameters" dialog.


Save contents of current directory to archive.rar. Store identical files larger than 1000000 bytes as references.

WinRAR a -oi:1000000 -ma archive