Acronis products save backup data in the proprietary TIB format using compression that reduces the amount of storage space needed for backups. Compression is used both in Windows and Linux operating systems and in Acronis Bootable Media.

Effective data compression level and resulting archive size depends on the type of files stored in the backup: even maximum compression cannot significantly reduce the backup size if the backup contains already compressed files, like .jpg, .pdf or .mp3. However, formats such as .doc or .xls will be compressed well.

You can choose the compression level for a backup in Backup options. For most products, the compression levels are:

• None - the data is copied without any compression, which may significantly increase the backup file size (especially with sector-by-sector backup);
• Normal - the recommended data compression level (set by default);
• High - higher backup file compression level, takes more time to create a backup;
• Maximum - maximum backup compression, but takes a long time to create a backup.

Acronis products use two libraries for compression: zlib, zstd and Acronis compression algorithm.

Archives of 'version 12' backup format and the new archive format in Acronis True Image use zstd, archives of 'version 11' backup format use zlib (Disk and partition backup with compression rates other than Normal; File and folder backup) and Acronis compression algorithm (Disk and partition backup: Normal compression rate).

Zlib and zstd are third-party compression library.

Compression ratio example

Example of compression ratio for different compression levels and different data types.

Acronis True Image Home 2021/2020:

Acronis Cyber Protect 15, Acronis Cyber Backup 12.5:

Acronis Backup & Recovery 10, Acronis Snap Deploy 3: