Apparently, Apple documentation can't keep up with App Store changes. Until today, the biggest (optional) display size was a 5.8-Inch Super Retina Display with a resolution of 1125 x 2436 pixels. Currently, it is a 6.5-inch display, but the resolution is nowhere to be found (docs at https://help.apple.com/app-store-connect/#/devd274dd925 only mention 5.8-inch display). App store connect doesn't mention the resolution and error message "The dimensions of one or more screenshots are wrong. Learn More." redirects to docs linked above.
New size is 1242 × 2688 pixels
Extra information for required sizes:
But iPhone XR doesn't have such resolution (it's
828x1792
).6.5 inch (iPhone XS Max, iPhone XR) 1242 x 2688 pixels (portrait) 2688 x 1242 pixels (landscape)
help.apple.com/app-store-connect/#/devd274dd925If you're using the Simulator, I found that only the iPhone XS Max gave
1242 x 2688
out of the box.Adding to what @LordParsley said, the simulator for Iphone 11 Pro Max also gave
1242 x 2688
resolution1284x2778 - add iphone 12 pro max size
It is quite weird why don't they just put the actual sizing in Appstoreconnect? Now we need to visit this stackoverflow answer everytime we are making screenshots. Thanks Apple :/