Whether you have a Word document, Excel workbook, MP3 song, a video or any other type of file or files contained in a ZIP file that you or someone else created, the process of extraction is the same. All recent versions of both Windows and Mac OS X include the ability to unzip archives without any additional software, but programs are available specifically for this job.
Open ZIP Archives in Windows
Double-click a ZIP file in Windows to open it. Windows displays ZIP archives as if they were folders, but if you're using the Details view mode, you'll see a few unique columns including Compressed Size and Password Protected.
To unzip a file from a ZIP archive, drag it out of the window into any other folder or onto the desktop. Windows 8 also offers an Extract tab while working with zipped files. Select a file and choose a folder from the Extract To section to unzip the file to a location on your computer.
Extract All Files in Windows
Click Extract All in the Extract tab to unzip the entire archive at once. (In Windows 7, the button is labeled Extract All Files instead.) Alternatively, right-click the ZIP file itself and choose Extract All. Whichever method you use, you'll reach the same window.
Change the destination, if necessary -- Windows defaults to the ZIP file's location -- and then check Show Extracted Files When Complete if you want a window to open showing the files. Click Extract to unzip the entire archive. Afterwards, you can delete the ZIP file itself without affecting the unzipped files.
Unzip Files on a Mac
Mac OS X makes the process even simpler than Windows. In either Mavericks or Yosemite, just double-click a ZIP file to extract its contents into the same folder as the ZIP file. If the ZIP file contains multiple files, OS X places them in a folder bearing the ZIP file's name. After unzipping, you can delete the ZIP file without losing the extracted files.
If you work with ZIP files frequently and don't like your system's built-in utility, or you need to create password-protected ZIP files in Windows, install another compression application. Two of the most popular options for Windows are WinRAR and WinZip, both shareware programs. For a completely free, though not quite as user-friendly option, try 7-Zip instead. These programs also support additional formats that Windows can't open on its own, including RAR and 7Z.
Free options for OS X include The Unarchiver, iZip, which also offers an iOS version, and StuffIt Expander, one of the oldest and best-known Mac extraction utilities. Expander also has a paid companion program, Stuffit Deluxe, for creating and sending archives.