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Windows uses file extensions such as .txt, .jpg, and .pdf to decide which application opens a file. If the wrong program launches—or Windows displays a prompt every time—you can change the association from Settings > Apps > Default apps.
The instructions below apply to Windows 11 and Windows 10. Windows 10 still runs after its support ended on October 14, 2025, but Microsoft no longer provides standard security fixes, technical assistance, or free Windows Update software updates for it.
Change the default app for a file extension in Settings
This is the current Microsoft-documented method for changing the association for an entire file type. It works for extensions such as .txt, .pdf, .jpg, .mp4, and .docx.
- Open Settings. You can press
Windows + I. - Select Apps, then select Default apps.
- Click the search field labeled Search apps or set defaults for file types or link types.
- Enter the extension, including the period. For example, enter
.txt, nottxt. - Select the result for that file type.
- Choose the application you want Windows to use, then confirm the change if Windows displays a confirmation prompt.
From that point forward, double-clicking a file with that extension should open it in the selected application. Existing files do not need to be renamed.
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Examples
| Extension | Possible default application |
|---|---|
.txt |
Notepad, Notepad++, or another text editor |
.pdf |
Microsoft Edge, Adobe Acrobat, or another PDF reader |
.jpg |
Photos, Paint, or an image editor |
.mp4 |
Media Player, VLC, or another video player |
.html |
Microsoft Edge, Chrome, Firefox, or another browser |
Change associations from an installed application
The same Default apps page can also be used from the application side:
- Open Settings > Apps > Default apps.
- Use the application list or search for the application’s name.
- Select the application.
- Select the file extension or link type you want to change.
- Choose the preferred application.
This view is useful when you want to review the extensions and protocols currently associated with one program rather than search for each extension separately.
Use File Explorer for a quick change
File Explorer is convenient when you are already looking at a file. It presents compatible applications and lets you browse for a program that Windows has not listed.
- Right-click the file.
- Select Open with > Choose another app.
- Select the application you want to use.
- If available, select the option to always use that application for this type of file, then confirm.
If the program is not listed, select Choose an app on your PC and browse to its executable file. For example, this may be an .exe file in C:Program Files or C:Program Files (x86).
This route is useful for opening a particular file and choosing a handler. For a deliberate, persistent file-type change, Microsoft’s documented route is still Settings > Apps > Default apps.
Find an application for an unfamiliar extension
If Windows does not know which program can open a file:
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- Right-click the file in File Explorer.
- Select Open with > Search the Microsoft Store.
- Select OK.
Windows can search the Microsoft Store for a compatible application. You can also use Choose an app on your PC if you already have suitable software installed.
Check the file extension before changing anything
If extensions are hidden, you may mistake a file’s name for its type. Windows filenames have a base name and an extension separated by a period—for example, report.txt. The extension helps determine the file type, icon, and application used to open it.
Changing a filename from report.txt to report.docx does not convert the file. It only changes the name. The contents remain a text file and may not open correctly in Word. Use the original application’s Save As or Export feature when you need a genuine format conversion.
Change an association with Command Prompt
Windows also includes the assoc and ftype commands. These are Command Prompt commands, not native PowerShell commands. Open Command Prompt when using them, or invoke them from PowerShell with cmd /c.
View the current association
Open Command Prompt and run:
assoc .txtThe result shows the file-type name mapped to .txt. To list all extension associations, run:
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assocThe association has two parts:
assocmaps an extension, such as.log, to a file-type name.ftypedefines the command Windows uses to open that file type.
Therefore, assoc by itself does not identify the executable that launches the file.
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Set or remove an extension mapping
To map .log to the existing txtfile file type, run:
assoc .log=txtfileTo remove the association for .bak, run:
assoc .bak= Microsoft specifies a space after the equal sign when removing an association. Association changes require administrator privileges, so open Command Prompt with Run as administrator if Windows rejects the command.
View or set the open command
To list file types that have open-command strings, run:
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ftype txtfileYou can define a file type and its command with commands such as:
assoc .pl=PerlScript
ftype PerlScript=perl.exe %1 %*In an ftype command, %0 or %1 is replaced by the launched file name. %* represents all parameters, while %2, %3, and later variables represent additional parameters.
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To delete the open command for a file type, use:
ftype example=Be careful when manually defining commands. An incorrect executable path, missing quotation marks around a path containing spaces, or an unsuitable command can make the association fail. For most users, the Settings interface is safer because it maintains the association through Windows’ normal default-app system.
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Run the commands from PowerShell
If you are already in PowerShell, call the commands through Command Prompt:
cmd /c assoc .txt
cmd /c ftype txtfileTyping assoc or ftype directly into PowerShell does not work because Microsoft documents both commands for cmd.exe.
Fix common problems
The extension cannot be found in Default apps
Enter the extension exactly, including its leading period. Search for .txt, not txt. If Windows has no association entry for the extension, the search may not return a usable file-type result. In that case, right-click a file with the extension and use Open with > Choose another app.
The application is installed but does not appear
Windows may not have registered the application as a compatible handler. In File Explorer, right-click the file, select Open with > Choose another app, then select Choose an app on your PC and locate the program’s executable.
The file still opens in the old application
Check that you changed the correct extension. A program may handle several related types—for example, .jpg, .png, and .gif—and changing one does not automatically change the others. Search for each extension separately in Default apps.
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Also check whether you are opening a shortcut, web link, or file inside another application. Link types and protocols, such as http and https, have their own default associations and are not controlled by the .html file association.
Changing the extension did not solve the problem
Renaming an extension is not a conversion and does not change the file’s internal format. Rename the file back to its original extension, then open or export it with software that supports the required format.
Which method should you use?
| Situation | Best method |
|---|---|
| You want every file of a type to use another program | Settings > Apps > Default apps, then search for the extension |
| You are handling one file in File Explorer | Open with > Choose another app |
| The program is installed but missing from the list | Choose an app on your PC |
| You need to inspect or script extension mappings | assoc and ftype in Command Prompt |
| The file has no known handler | Open with > Search the Microsoft Store, or browse to an installed program |
FAQ
How do I change the default app for a file type in Windows 11?
Open Settings, go to Apps > Default apps, search for the extension including its period—for example, .pdf—and select the application you want Windows to use.
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No. Microsoft’s current instructions use the search field on Settings > Apps > Default apps. The older wording belongs to previous Windows 10 guidance.
Can I set a default app from File Explorer?
Yes. Right-click a file and select Open with > Choose another app. If the program is missing, select Choose an app on your PC and browse to its executable.
Why does assoc not change the application by itself?
assoc maps an extension to a file-type name. The open command for that file type is defined separately with ftype.
Can I run assoc and ftype in PowerShell?
Not as native PowerShell commands. Run them in Command Prompt, or use cmd /c assoc and cmd /c ftype from PowerShell.
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No. Renaming changes only the filename extension. It does not convert the file’s contents or internal format.
The Bottom Line
For normal Windows use, open Settings > Apps > Default apps, search for the complete extension such as .pdf, and select the preferred application. Use File Explorer when choosing a handler for a file in front of you, and reserve assoc and ftype for command-line inspection or deliberate configuration.
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