# New RAR 5.0 archiving format. You can use “RAR 5.0” option in archiving dialog or -ma command line switch to create RAR 5.0 archives. Older software including older WinRAR versions is not able to decompress RAR 5.0 archives, so if you plan to send an archive to other people, it is necessary to take the compatibility issue into consideration. You can select “RAR” instead of “RAR5” option in archiving dialog to create RAR 4.x archives compatible with previous WinRAR versions.
# Changes in RAR 5.0 compression algorithm:
* maximum compression dictionary size is increased up to 1 GB in 64 bit WinRAR. 32 bit WinRAR version can use up to 256 MB dictionary when creating an archive. Both 32 bit and 64 bit versions can unpack archives with any dictionary size, including 1 GB;
* default dictionary size for RAR 5.0 is 32 MB, typically resulting in higher compression ratio and lower speed than RAR 4.x 4 MB. You can use “Dictionary size” archiving dialog option or -md switch to change this value;
* -md switch syntax is modified to support larger dictionary sizes. Append ‘k’, ‘m’ and ‘g’ modifiers to specify the size in kilo-, mega- and gigabytes, like -md64m for 64 MB dictionary. If modifiers are not present, megabytes are assumed, so -md64m is equal to -md64;