What is the difference between rar and RAR5 compression?

Solution 1:

When you're choosing a compression type in WinRAR, "RAR" uses v2.9 (sometimes referred to as v4) of the algotrithm, where selecting "RAR5" uses v5. Both are detailed in the wiki article, which others have already linked to.

RAR5 supports some additional encryption features, but you're asking which one is better for compression - from the wiki, it looks like RAR5 might by trivially better for compression speed and smaller in some very specific cases, but the advantages appear to be all on the side of the viewer/decompressor:

• Improved damaged archive recovery
• Improved file table (meaning quicker browsing of an archive)
• Multicore decompression support

In exchange, you're taking the chance that the end user won't have a program that supports the new format, and won't be able to decompress your archive. However, if you're keeping the archive for yourself or you're sending it to somebody that you know has a program that can view it, it looks like RAR5 is the better format.

Solution 2:

There isn't a difference.

RAR is the overal compression schema.

RAR5 is the revision of the compression schema

RAR is a proprietary archive file format that supports data compression, error recovery and file spanning. It was developed by a Russian software engineer, Eugene Roshal (the name RAR stands for Roshal Archive) and the RAR software is licensed by win.rar GmbH.

v5.0 - supported by WinRAR 5.0 and later. Changes in this version:

• Maximum compression dictionary size increased to 1 GiB (default for WinRAR 5.x is 32 MiB and 4 MiB for WinRAR 4.x).
• Maximum path length for files in RAR and ZIP archives is increased up to 2048 characters.
• Support for Unicode file names stored in UTF-8 format.
• Faster compression and decompression.
• Multicore decompression support.
• Greatly improves recovery.
• Optional AES encryption increased from 128-bit to 256-bit.
• Optional 256-bit BLAKE2 file hash instead of a default 32-bit CRC32 file checksum.
• Optional duplicate file detection.
• Optional NTFS hard and symbolic links.
• Optional Quick Open Record. Rar4 archives had to be parsed before opening as file names were spread throughout the archive, slowing operation particularly with slower devices such as optical drives, and reducing the integrity of damaged archives. Rar5 can optionally create a "quick open record", a special archive block at the end of the file that contains the names of files included, allowing archives to be opened faster.
• Removes specialized text, multimedia, and Itanium executables compression algorithms; consequently some files of these types compress better with WinRAR 4.x (Rar4) than WinRAR 5.x (Rar5).

RAR (file format)