The 7z format is a form of file compression designed to make a large file smaller, for easier storage or sharing. As of publication, Windows doesn't feature built-in support for the 7z format like the ZIP format. In order to decompress and open 7z files, you need a separate program designed to handle them.
7Zip is generally the standard, as it was the first 7z program and written by the creator of the 7z format for decompressing 7z files. WinRar and WinZip are reliable alternatives that cover more file types than 7Zip. 7Zip is, however, the only completely free choice of the three.
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With each of the decompression apps described above, your right-click menu gains a few new options designed to make decompression more convenient. All 7Zip and WinZip options are listed under the 7Zip and WinZip flyout menus respectively, while WinRAR options are added directly to the right-click menu. Each of these options works in a slightly different way, as follows:
Open Archive is a 7Zip-only option that launches a window of that app and opens the file but doesn't extract the file.
Open With WinRAR is a WinRAR-only option that works in the same fashion as Open Archive for 7Zip.
WinZip doesn't have a right-click option comparable to Open Archive or Open With WinRAR.
Extract Files... opens the file with the file extraction utility, offering options on where to save the file and how to extract. This option is available with all three apps.
Extract Here immediately extracts all files to the same folder as the 7z file. This option is available with all three apps.
Extract To followed by the filename and a slash immediately creates a new folder with that name and extracts all files into that folder. For example, if the file name is Sample, then this option would appear as Extract to Sample. This option is available with all three apps.
Each app's method of decompression within the app window is slightly different.
For 7Zip, right-click the file and select Open Archive, then select the file(s) you want to decompress. Click the Extract button then type the path for the file's destination folder if desired -- otherwise, a new folder containing the files is created in the same location as the 7z file. Click OK and wait for the file to finish extracting.
For WinRAR, right-click the file and select Open with WinRAR, then select the file(s) you want to decompress. Click Extract to and enter the file path for the destination location if desired, then click OK.
For WinZip, start up WinZip and click File, followed by Open (from PC/Cloud). Set the drop-down menu to All archives, then find and select the file and click Open. Select the file(s) you want to extract using the check boxes, then click Unzip Selected Files followed by Unzip.
Files compressed in the 7z format can be encrypted for additional security or broken down into several pieces to make them easier to share. This does potentially create some hurdles when you receive these files from a website or another person.
To unlock encrypted files, enter the password when prompted during decompression. Passwords are case-specific so make sure your capslock isn't turned on.
To decompress a file broken into multiple pieces, start by decompressing the first piece of the file and make sure all the subsequent pieces are in the same folder. The first piece is usually distinguishable from the others by its file extension, which adds .001. For example, the first piece of a broken-up archive named Sample would be Sample.7z.001.