Files ending in .7z are compressed archives created with Igor Pavlov's free 7-Zip open source packaging program. 7-Zip uses the open-source LZMA compression method, but can also use LZMA2, PPMd or BZip2. 7Z is next to .zip and rar the most common pack formats.
The LZMA compression method has a high compression rate and can also be provided with the strong AES-256 (256-bit) encryption, whereby the file names can be encrypted. The price for the high compression rate is a longer packing time.
The 7Z archive format can contain unicode file names (for example, Korean or Chinese characters) and has a maximum file size of 16,000,000,000 GB. Standard archives created with 7-Zip contain recovery data to repair the archive in case of corruption.
But you can also create so-called solid archives, which are sometimes considerably smaller (depending on the archived data), but contain no recovery data.
Most often resolving problems with opening 7Z files is very simple. Just install an appropriate program that supports such files. All of the listed programs support 7Z files, but may vary in offered function and purpose. Some programs may be capable only of viewing contents of 7Z files or offer file conversion options, but may not be capable of editing such files.
It is possible that although a compatible program has been installed on user’s system, it is not used by the system to open it. This may happen because no default application was associated with this type of files. To associate 7Z files with given application, select "Open with" from drop-down menu (accessed by right-clicking on the file). Then select from the list the program or application you want to be used to open this type of file. If the WinZip applications is not on the list, select "Browse" option in order to manually locate the directory where WinZip has been installed.
Sometimes problems with opening 7Z files may not lie with the application itself, but can arise due to other causes, such as: