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7z archive format

7z format was developed by Igor Pavlov and announced in 1999.

And, LZMA and LZMA2, which are very powerful compression algorithms, are used in 7z format. They are also published as open-source(public domain) so they are used widely in other archive formats.

Pros of 7z

7z is a comparatively recent archive format compared to other legacy archive formats. So this format has these advanced features.

  • 7z supports LZMA/LZMA2 compression algorithms of high compression ratio. In particular, LZMA2 compression is an improved algorithm of LZMA for supporting multi-thread.
  • 7z supports advanced encryption method(AES256)
  • Filename encryption. Without the password, you can't even access filenames in the archive.
  • Solid compression, Unicode filenames, large file support over 4GBytes and so on.

Cons of 7z

7z uses various ways, including header compression, to make a small archive file, so it boasts a high compression ratio.

However, because of this characteristics, it is almost impossible to recover a file which is damaged in any way.

Therefore, please be careful not to damage files when you backup your important files in 7z format.

Information on how to recover damaged 7z files can be found below, but successful recovery is extremely limited even for professionals.


Characteristics of 7z created by Bandizip

Bandizip creates 7z archive files with its own compression module based on LZMA SDK.

So, when you compress a 7z file with Bandizip, the archive file's characteristics will differ from files made on 7-zip as below:

  • Bandizip creates a 7z file with only one solid block.
  • File encryptions will also encrypt archive header too.
  • Bandizip supports LZMA2 only.