Windows file names have two parts separated by a period: first, the file name, and second, a three- or four-character extension that defines the file type. In expenses.xlsx , for example, the first part of the file name is expenses and the extension is xlsx . Extensions tell your computer which application created or can open the file and which icon to use for the file. For example, the docx extension tells your computer that Microsoft Word can open the file and to display a Word icon when you view it in File Explorer. Most file name extensions are compatible with more than one program that you have installed. You can change a file name extension, but that won't convert the file to another format or change anything else about it except the file name. To learn more about how to change which program will open a file, read Change default apps in Windows . If you don’t see file name extensions when you view files in File Explorer: In the search box on the taskbar, type file explorer , and in the search results, select File Explorer . In the search box on the taskbar, type file explorer , and in the search results, select File Explorer . In File Explorer, select View > Show > File name extensions . In File Explorer, select View > Show > File name extensions . Common file name extensions Below is a list of common Windows file name extensions and formats. Open unknown file extensions Microsoft Store: Click Start , type Microsoft Store, and press Enter . Type the file extension name in the search window and press Enter to find any compatible apps. If you don't know the file extension name, right-click the file, select Open with > Search the Microsoft Store , and click OK . Microsoft Store will list any apps that can open the file. Right-click the file and select Open with > Choose another app to see a list of apps on your computer. Select any of these to try to open the file or select Choose an app on your PC to find other installed apps. Notepad, Adobe Acrobat Pro, or Adobe Acrobat Reader can open any type of document format (text). Windows Media Player can open many video file formats, and Windows Photo app can open many photo formats. Support for Windows 10 has ended on October 14, 2025 After October 14, 2025, Microsoft will no longer provide free software updates from Windows Update, technical assistance, or security fixes for Windows 10. Your PC will still work, but we recommend moving to Windows 11. Windows file names have two parts separated by a period: first, the file name, and second, a three- or four-character extension that defines the file type. In expenses.xlsx , for example, the first part of the file name is expenses and the extension is xlsx . Extensions tell your computer which application created or can open the file and which icon to use for the file. For example, the docx extension tells your computer that Microsoft Word can open the file and to display a Word icon when you view it in File Explorer.

Most file name extensions are compatible with more than one program that you have installed. You can change a file name extension, but that won't convert the file to another format or change anything else about it except the file name. To learn more about how to change which program will open a file, read Change default apps in Windows . If you don’t see file name extensions when you view files in File Explorer: In the search box on the taskbar, type file explorer , and in the search results, select File Explorer . In the search box on the taskbar, type file explorer , and in the search results, select File Explorer . In File Explorer under View , in the Show/hide group, select the File name extensions check box. In File Explorer under View , in the Show/hide group, select the File name extensions check box. Common file name extensions Below is a list of common Windows file name extensions and formats. Open unknown file extensions Microsoft Store: Click Start , type Microsoft Store, and press Enter . Type the file extension name in the search window and press Enter to find any compatible apps. If you don't know the file extension name, right-click the file, select Open with > Search the Microsoft Store , and click OK . Microsoft Store will list any apps that can open the file. Right-click the file and select Open with > Choose another app to see a list of apps on your computer. Select any of these to try to open the file or select Choose an app on your PC to find other installed apps. Tip Notepad, Adobe Acrobat Pro, or Adobe Acrobat Reader can open any type of document format (text). Windows Media Player can open many video file formats, and Windows Photo app can open many photo formats. Right-click the file and select Open with > Choose another app to see a list of apps on your computer. Select any of these to try to open the file or select Choose an app on your PC to find other installed apps. Notepad, Adobe Acrobat Pro, or Adobe Acrobat Reader can open any type of document format (text). Windows Media Player can open many video file formats, and Windows Photo app can open many photo formats. Open XML formats and file name extensions File formats that are supported in Windows Media Player File formats that are supported in Excel File formats that are supported in PowerPoint File formats that are supported in Project Thank you for your feedback!