The iPad Pro 12.9" Wallpaper size (2048×2732px)
2048x2732 pixels is the native portrait resolution of the 12.9-inch iPad Pro, a large 3:4 Liquid Retina display. A wallpaper at this exact size fills the panel edge to edge with no upscaling, so photos and artwork stay razor sharp on one of the highest-quality tablet screens Apple makes.
The 3:4 ratio is far boxier than a phone's tall shape, and unlike a phone an iPad rotates, so the same wallpaper must also work in landscape when the device is turned. That is why a phone or desktop wallpaper never fits an iPad well; resizing to a native 2048x2732 respects the tablet's proportions in portrait, which is the orientation the Home Screen and lock screen use by default.
Because the iPad Pro's panel is large and dense, use a high-resolution source at or above 2048x2732 so detail holds up; a smaller image will look soft when scaled to this big screen. Plan for the interface: the lock screen shows a large clock in the upper-middle, and the Home Screen arranges a grid of app icons and widgets across the display. Keep the focal point centered so it works whether the iPad is held upright or rotated, and reads well behind the icon grid. This tool resizes entirely in your browser, so even a large file is never uploaded, it is free, and your original quality is preserved while the image is fit to the 3:4 frame. Apple can change specs, so verify before exporting.