Follow these steps to set up Firefox to work with Android Assist, so that a Firefox search replaces Google Assistant when you long-press the home button. This Android Assist feature only works with Android 5 Lollipop and newer.

On Pixel XL and Android 8.1

1. Open the Settings app on your phone.
2. Tap Apps & Notifications.
3. Tap Advanced.
4. Tap Default Apps.
5. Tap Assist & voice input.
6. Tap Firefox.

You can now long-tap the home button to search with Firefox.

On Note 8 and Android 7.1.1

1. Open the Settings app on your phone.
2. Tap the menu on the top right.
3. Tap Default Apps.
4. Tap Device assistance app.
5. Tap Firefox.

You can now long-tap the home button to search with Firefox.