Frequently Asked Questions (FAQ)

Yes, 1-Zip is free software. You can use it on any computer. You don't need to register or pay for 1-Zip.

You must run 1-Zip File Manager in administrator mode. Right-click the icon of 1-Zip File Manager, and then click Run as administrator. Then you can change file associations and some other options.

Old versions of 1-Zip (before version 15.06) used file sorting "by type" ("by extension").

The new version of 1-Zip supports two sorting orders:

• sorting by name - default order.
• sorting by type, if 'qs' is specified in Parameters field in "Add to archive" window, (or -mqs switch for command line version).

You can get big difference in compression ratio for different sorting methods, if dictionary size is smaller than total size of files. If there are similar files in different folders, the sorting "by type" can provide better compression ratio in some cases.

Note that sorting "by type" has some drawbacks. For example, NTFS volumes use sorting order "by name", so if an archive uses another sorting, then the speed of some operations for files with unusual order can fall on HDD devices (HDDs have low speed for "seek" operations).

You can increase compression ratio with the following methods:

• Specify 'qs' in Parameters field (or use -mqs switch for command line version).
• Increase dictionary size. It can help when 'qs' is not used.

If you think that unusual file order is not problem for you, and if better compression ratio with small dictionary is more important for you, use 'qs' mode.

In 99% of these cases, it means that the archive contains incorrect headers. Other ZIP programs can open some archives with incorrect headers since these programs just ignore errors.

If you have such an archive, please don't contact the 1-Zip developers about it. Instead, try to find the program that was used to create the archive and inform the developers of that program that their software is not ZIP-compatible.

There are also some ZIP archives that were encoded with methods unsupported by 1-Zip, for example, WAVPack (WinZip).

1-Zip 9.20 supports RAR 2/3/4 formats only and doesn't support RAR5 archives. However, the latest versions of 1-Zip support RAR5 archives.

1-Zip doesn't know the folder path of the drop target. Only Windows Explorer knows the exact drop target. And Windows Explorer needs files (drag source) as decompressed files on the disk. So 1-Zip extracts files from the archive to a temp folder, and then 1-Zip notifies Windows Explorer about the paths of these temp files. Then Windows Explorer copies these files to the drop target folder.

To avoid temp file usage, you can use the Extract command of 1-Zip or drag-and-drop from 1-Zip to another instance of 1-Zip.

You're probably using a *.* wildcard. 1-Zip doesn't use the operating system's wildcard mask parser and consequently treats *.* as any file that has an extension. To process all files, you must use the * wildcard instead or omit the wildcard altogether.

32-bit Windows allocates only 2 GB of virtual space per application. Additionally, this block of 2 GB can be fragmented (for example, by some DLL files), making it impossible for 1-Zip to allocate one large contiguous block of virtual space. There are no such limitations in 64-bit Windows. Therefore, you can use any dictionary size in Windows x64, provided you have the required amount of physical RAM.