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To change which program opens a file type in Windows, go to Settings > Apps > Default apps, search for its extension (such as .txt) or link protocol, and select an available app. If you already have a file in File Explorer, use Open with to choose an app for that file or set the default for its type.
Choose the right way to change a default
| Route | Best when | What you can do |
|---|---|---|
| Settings > Apps > Default apps | You know the file extension or link protocol, or want to inspect an app’s supported types. | Choose an app for a file type or protocol, or select an app and review the types it handles. Microsoft documents this route for Windows 10 and Windows 11. |
| File Explorer > Open with | You are looking at a representative file and want to try an app or set the default for its type. | Open the file once with an app or make that app the default for files of the same type. Microsoft’s Open with guidance explains the distinction. |
Change a default in Settings
- Open Settings.
- Select Apps > Default apps.
- Search for the file extension, including the leading period—for example,
.txt—or search for the relevant link protocol. - Select the result and choose one of the apps Windows offers.
The available choices depend on which apps are installed and registered to handle that type. If you start from an app instead, select it in Default apps to inspect the file types and link protocols it supports, then change the specific association you need. See Microsoft’s default-app instructions for the Windows 10 and Windows 11 procedures.
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Use Open with for a file in File Explorer
- In File Explorer, right-click a file of the type you want to open.
- Select Open with > Choose another app. The exact wording or dialog layout can vary by Windows version.
- Choose an app. Select the one-time option if you only want to open or test this file; use the always/default option only if you want that app to open files of this type in the future.
This is a file-first shortcut: choosing an app for one opening does not have the same scope as making it the default for the whole file type. Microsoft also documents keyboard navigation for the Open with flow in its default-app guidance.
Identify an unknown extension without mistaking it for a conversion
A filename usually has a name followed by an extension, separated by a period—for example, notes.txt. The extension helps identify the file type, but changing the extension only changes the name. As Microsoft Support explains, “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.” Renaming .jpg to .png, for example, does not convert the image data.
If you do not recognize an extension, Microsoft suggests searching the Microsoft Store for it or using Open with to see compatible apps already installed. A suggested app is not proof that a file is safe or that it is genuinely in the format its name claims: consider where an unfamiliar file came from before opening it. The available apps and their compatibility depend on your installation and the file’s actual format. See Microsoft’s extension guide.
If the right app is selected but the file still will not open
Changing the association tells Windows which app to launch. If that app opens but fails, crashes, or handles the file incorrectly, the issue may be the app rather than the association. For some apps, Windows provides repair controls:
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- Open Settings > Apps > Installed apps.
- Find the app, select its menu, and open Advanced options, if available.
- Select Repair. If Repair is unavailable or does not solve the problem, try Reset, if offered.
Repair and Reset are not available for every app, and Reset can affect app data or settings. Some desktop programs instead offer Repair or Change through Control Panel. Follow Microsoft’s repair guidance for the applicable app and Windows version.
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Microsoft’s default-app instructions cover both Windows 10 and Windows 11. The basic association setting remains documented for Windows 10; its availability does not mean the operating system remains supported. Microsoft states that Windows 10 support ended on October 14, 2025. The PC will continue to work, but Microsoft no longer provides free Windows Update software updates, technical assistance, or security fixes for Windows 10 after that date. See Microsoft’s file-extension article for the support notice.
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