What you will achieve

Set default apps for browsing, email, PDFs, and media on Windows 11 — including per-file-type overrides when the simplified defaults page is not enough.

1) Set defaults from Settings

Open Settings → Apps → Default apps.
Search for an app (e.g. Chrome, Firefox, Adobe Acrobat) and set it as default for linked file types and protocols.
Or pick a file type (e.g. .pdf, .htm) from the list and assign the preferred app.

2) Override from File Explorer

Right-click a file → Open with → Choose another app.
Select the app, tick Always use this app to open .ext files, click OK.

3) Reset corrupted defaults

In Default apps, scroll to the app misbehaving → click Reset if available.
Or reassign each extension manually — Windows 11 removed the old "Set defaults by app" single-click button from Windows 10.

4) Protocol handlers (mailto, http)

Default apps → Choose defaults by link type or search "HTTP" / "MAILTO" in Default apps.
Assign browser and mail client — fixes links opening the wrong app from Office or Teams.

5) Export default associations (Pro)

dism /online /Export-DefaultAppAssociations:C:\Temp\defaults.xml on golden image PC.
Import via Group Policy: Computer Configuration → Administrative Templates → Windows Components → File Explorer → Set a default associations configuration file.

6) Browser choice popup

Windows 11 may prompt after updates to confirm browser — set once per user profile to stop nagging.

7) MAILTO and calendar defaults

Settings → Apps → Default apps — search Mail, Calendar, and Browser separately; Windows 11 splits protocols more granularly than Windows 10.

8) Per-protocol edge cases

.pdf, .html, HTTP, HTTPS, MAILTO must be set separately on Windows 11 — setting Chrome as browser does not auto-set PDF handler.
Adobe Reader vs browser PDF plugin — pick one deliberately for security patching path.

Verification checklist

Click mailto: link in browser — opens chosen mail app. Open sample.pdf from Explorer — correct PDF handler. Repeat after feature updates which reset defaults sometimes.

Reboot once after changes that affect services, drivers, or firmware.
Confirm the original problem is resolved under normal daily use, not only immediately after the fix.
Note date, Windows version (Settings → System → About), and what changed in your personal runbook for next time.

Quick reference paths

Settings → Apps → Default apps
ms-settings:defaultapps
Default apps by file type
Admin tools: press Win + X for Terminal (Admin), Device Manager, and Computer Management.