Grey square as notification icon using Firebase notifications

Question

I am attempting to integrate Firebase Cloud Messaging into my android app. But when the app is in the background or closed, Firebase notification is displayed with grey squa

Answer 1

Create the base shape within a 25x25 px image on a transparent background. Mind the safeframe, and keep the upper and lower 2 pixels free. Export the icon at 25x25 as a PNG file with transparency enabled.