The recommended size for a Facebook cover photo is 820 pixels wide by 312 pixels tall on desktop and 640 pixels wide by 360 pixels tall on mobile devices. Its important to note that Facebook will crop the photo differently on desktop and mobile devices, so its recommended to keep all text and graphics within the middle safe zone to ensure that none of the critical components of the cover photo are getting cut off on either device. Additionally, the image must be at least 400 pixels wide by 150 pixels tall to align with Facebooks requirements. Its also recommended to use a sRGB JPG file that is 851 pixels wide by 315 pixels tall and less than 100 kilobytes to ensure that the image loads quickly.