A decent file archiver, compresses and extracts a variety of archive and file types!
Yes, 7-Zip is free software. You can use it on any computer. You don't need to register or pay for 7-Zip.
You must run 7-Zip File Manager in administrator mode. Right-click the icon of 7-Zip File Manager, and then click Run as administrator. Then you can change file associations and some other options.
Like most free software, 7-Zip’s support is limited. Although it includes a built-in user guide and online forums, there is no active customer support through email or telephone. However, found that the forums are active and many of your questions can be answered there.
Now there one main version of 7-Zip: 7-Zip 9.20 - it's revision 20 of 7-Zip 9 (started in 2009)
Latest beta versions can fix some bugs of previous versions. So they can be more stable in some cases. In general it's safe to use latest beta version.
These operations didn't work only in old versions of 7-Zip. Latest 7-Zip supports any operations with "solid" archives.
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 archive, please don't call the 7-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 7-Zip, for example, WAVPack (WinZip).
Why does drag-and-drop archive extraction from 7-Zip to Explorer use temp files?
7-Zip doesn't know folder path of drop target. Only Windows Explorer knows exact drop target. And Windows Explorer needs files (drag source) as decompressed files on disk. So 7-Zip extracts files from archive to temp folder and then 7-Zip notifies Windows Explorer about paths of these temp files. Then Windows Explorer copies these files to drop target folder.
To avoid temp file usage, you can use Extract command of 7-Zip or drag-and-drop from 7-Zip to 7-Zip.
You're probably using a . wildcard. 7-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.
In most cases you don't need -r switch. 7-Zip can compress subfolders even without -r switch.
7z.exe a c:a.7z "C:Program Files"
compresses "C:Program Files" completely, including all subfolders.
7z.exe a -r c:a.7z "C:Program Files"
searches and compresses "Program Files" in all subfolders of C: (for example, in "C:WINDOWS"). If you need to compress only files with some extension, you can use -r switch: 7z a -r c:a.zip c:dir*.txt
compresses all *.txt files from folder c:dir and all it's subfolders.
7-Zip stores only relative paths of files (without drive letter prefix). You can change current folder to folder that is common for all files that you want to compress and then you can use relative paths: cd /D C:dir1 7z.exe a c:a.7z file1.txt dir2file2.txt
32-bit Windows allocates only 2 GB of virtual space per one application. Also that block of 2 GB can be fragmented (for example, by some DLL file), so 7-Zip can't allocate one big contiguous block of virtual space. There are no such limitations in 64-bit Windows. So you can use any dictionary in Windows x64, if you have required amount of physical RAM.
For exe installer: Use the "/S" parameter to do a silent installation and the "/D=dir" parameter to specify the "output directory". These options are case-sensitive. 7-Zip uses the NSIS installer by Nullsoft.
For msi installer: Use the /q INSTALLDIR="C:Program Files7-Zip" parameters.