Default Apps and File Associations: Choosing What Opens Your Files

What “Default Apps” and “File Associations” Mean

Windows uses file associations to decide which app opens a file when you double-click it. A file association links a file type (usually identified by its extension) to a specific app.

• .pdf → a PDF reader (for example, Microsoft Edge or Adobe Acrobat Reader)
• .jpg / .png → a photo viewer/editor (for example, Photos)
• .docx → a word processor (for example, Word)
• .html and http/https links → a web browser (for example, Edge, Chrome, Firefox)

When you double-click a file, Windows checks the file extension and launches the app currently set as the default for that type. If you change the default, future double-clicks use the new app.

File extensions: how to recognize them

The extension is the part after the last dot in a filename, like report.pdf or photo.jpg. If you don’t see extensions in File Explorer, you can still change defaults using Settings or the file’s Open with menu, but seeing extensions makes it easier to understand what you’re changing.

How Windows Chooses the Default App

Windows maintains a list of defaults in Settings. Defaults can be set in different ways:

• By file type (example: set .pdf to open with a specific app)
• By link type/protocol (example: set HTTP and HTTPS to open with a specific browser)
• By “default app” category (browser, email, music player, photo viewer, etc.—availability varies by Windows version)

Some apps will also ask to become the default when you first open them or during setup. If you accept, Windows updates the association.

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Change Default Apps Using Settings (Recommended)

Use Settings when you want a clean, system-wide change.

Option A: Change the default for a common category (like Browser)

Steps (Windows 11 style):

1. Open Settings.
2. Select Apps > Default apps.
3. To change your browser: find Web browser (or search for your preferred browser app name).
4. Select the current default and choose the browser you want.

Note: On some Windows 11 builds, you may need to confirm multiple related defaults (such as HTTP, HTTPS, .htm, .html). Windows may guide you through these.

Option B: Set defaults by file type (best for PDFs and images)

Steps:

1. Open Settings > Apps > Default apps.
2. In the search box, type the extension you want to change (for example, .pdf or .jpg).
3. Select the extension from the results.
4. Choose the app you want to use by default.

Practical examples:

• Set .pdf to open with Adobe Acrobat Reader (if installed) instead of Edge.
• Set .jpg and .png to open with Photos (or another viewer) consistently.

Option C: Set defaults by app (useful when you want one app to own many types)

Steps:

1. Open Settings > Apps > Default apps.
2. Select an app (for example, your PDF reader or photo editor).
3. You’ll see file types and link types that app can handle.
4. For each type you care about, select it and choose that app.

This is helpful if you want one app to open multiple image types (like .jpg, .png, .gif) without changing them one by one via extension search.

Change Defaults from a File: “Open with”

Use this method when you’re already looking at a specific file and want to switch quickly.

Set a new default using “Open with”

1. Right-click the file (for example, a PDF or JPG).
2. Select Open with > Choose another app.
3. Select the app you want.
4. Check Always use this app to open .ext files (the wording varies).
5. Click OK.

After this, double-clicking that file type should open in the chosen app.

When Windows prompts you to pick an app

If Windows doesn’t have a default yet (or the association is broken), you may see a prompt like “How do you want to open this file?”

1. Select the app you want to use.
2. If available, check Always use this app.
3. Confirm to set it as the default for that file type.

Common Scenarios You’ll Actually Use

Scenario 1: Choosing a default browser

Why it matters: links from documents, apps, and Windows features open in your default browser.

• Change it in Settings > Apps > Default apps > Web browser.
• If Windows asks you to confirm or set additional link/file types, follow the prompts so links open consistently.

Scenario 2: Choosing a default PDF reader

PDFs often open in a browser by default. You might prefer a dedicated reader for features like annotations, signing, or better printing controls.

• In Settings, search for .pdf and set your preferred reader.
• Or right-click a PDF > Open with > choose the reader > set Always.

Scenario 3: Choosing a default photo viewer

If images open in an app you don’t like, set a consistent viewer for common image types.

• In Settings, search for .jpg and .png and set them to your preferred viewer.
• Consider also setting .jpeg, .gif, and .bmp if you use them.

How to Revert or Fix Defaults

Revert a single file type back to another app

Just change it again using either method:

• Settings > Apps > Default apps > search the extension and pick a different app.
• Or right-click a file > Open with and set a different default.

Reset defaults for an app (when available)

In Settings > Apps > Default apps, selecting an app shows what it handles. If you changed many types and want to undo them, switch those types back to another app one by one. (Some Windows versions also provide limited reset options depending on the app and category.)

If a file type is unknown or won’t open

An “unknown file type” usually means Windows doesn’t have an app installed that understands that format.

• Identify the extension (example: .heic, .7z, .psd).
• Right-click the file > Open with to see suggested apps.
• If nothing suitable appears, you need to install an app that supports that file type (for example, an archive tool for .7z, a codec/extension for .heic, or a design tool for .psd).
• After installing, return to Open with or Default apps to set it as the default.

If a file type used to open correctly but suddenly doesn’t, the association may have changed after an update or new app install. Reassign the default using Settings.

Practice: Change Defaults and Verify

Practice 1: Change the default browser (where permitted)

1. Open Settings > Apps > Default apps.
2. Change Web browser to your preferred browser.
3. Test: open any app that contains a link (or click a link in a document) and confirm it opens in the chosen browser.

Practice 2: Set a default app for PDFs

1. In Settings > Default apps, search for .pdf.
2. Select the current default and choose your preferred PDF app.
3. Test: find a PDF file and double-click it. Confirm it opens in the intended app.

Practice 3: Set a default app for images

1. In Settings > Default apps, search for .jpg and set your preferred viewer.
2. Repeat for .png (and optionally .jpeg).
3. Test: double-click a JPG and a PNG and confirm both open in the intended app.

Troubleshooting checklist (if the test doesn’t work)

• Make sure you changed the correct extension (for example, .jpeg vs .jpg).
• If you used Open with, confirm you checked Always use this app.
• Try changing the default in Settings (it’s more reliable for system-wide behavior).
• If the desired app doesn’t appear, it may not support that file type or may not be installed correctly.