You can set Firefox as your default browser from the Firefox Preview app on your Android device.

Android version 7 and newer

1. Tap the menu button
   
2. Tap Settings.
3. Tap the Set as default browser toggle.

   The DEFAULT DEVICES screen displays.

4. Tap Browser app.

   The BROWSER APP screen displays.

5. Tap the Firefox Preview radio button.

Android version 6

1. In the Settings menu on your device, tap Apps & notifications (it may be called Apps or Applications on some versions of Android).
2. Tap Advanced (you may have to tap on the Gear icon first on some versions of Android).
3. Tap Default apps.
4. Tap Browser app to open a list of choices.
5. Tap Firefox Preview to select it.

Android version 5 and older

Step 1: Clear the current browser that opens links

1. Open the Settings application and tap on Apps.

   On some versions of Android, this button is labeled Applications or Application manager and you may have to tap on Manage applications before the next step.

2. Tap on the All tab.

   

3. Tap on the current browser that opens links.

   This is usually the default browser which is called "Browser" or "Internet".

4. Tap on Clear defaults to prevent this browser from opening links by default.

   If you haven't installed another browser or you have installed another browser like Opera and set it as your default browser, then Clear defaults will be grayed out. If you have installed another browser, go back to the previous step and repeat with the default browser.

   

Step 2: Set Firefox Preview to be the default browser for opening links

1. Open a link in an Android application like the Mail application.
2. Tap on Firefox Preview and then tap on Always.