Android banner (push image) requirements

There is no one specific resolution or aspect ratio requirements, as there are many devices with different displays. Android can scale and crop images if necessary.
 
Basic suggestions:

• The recommended maximum file size is 1 MB for load-balance purpose and fast download.
• Almost any resolution is supported, around 1000×1000px looks fine. More than 2000×2000px isn't recommended due to the large file size.
• Supported formats include JPEG, PNG.
• Aspect ratio: nearly any aspect ratio is technically supported. While a 2:1 ratio is recommended, 16:9 and square are quite common too.
• The center-cropped image is recommended.

Please note that banner behavior is entirely controlled by the Android/User interface. Pushwoosh SDK by default contains the specific method for showing the pictures in the push, but the handling of it is passed to the operating system. For instance, the inconsistencies may be observed on some devices with custom UI (e.g., One UI, MIUI, etc.).

Also, please note that to be properly displayed, the message with a banner should be the very first in your Notification Bar, otherwise some parts of it (e.g., header or content) might be cropped.