The YouTube End Screen size (1280×720px)
A YouTube end screen is the final 5 to 20 seconds of a video where you place clickable elements that promote other videos, playlists, or a subscribe button. It uses the same 16:9 frame as the video itself, so a background image at 1280x720 pixels matches the standard HD canvas and lines up perfectly behind the interactive cards YouTube overlays on top.
The design challenge here is that end screens are mostly about the elements, not the picture. YouTube reserves specific regions for video thumbnails, the channel icon, and the subscribe circle, and those elements snap into a grid within the 16:9 area. Your background at 1280x720 should therefore leave clear, low-detail zones where those cards will sit, rather than filling every corner with busy artwork that competes with the clickable thumbnails viewers are meant to tap.
Matching the exact 1280x720 dimensions also avoids the letterboxing or stretching that happens when you drop a mismatched still into a 16:9 timeline. A calm background with an inviting call to action, such as an arrow pointing toward where a video card appears, guides the eye toward the next click. This tool resizes 100% in your browser with no upload, it is free, and it preserves the 16:9 aspect ratio. YouTube periodically changes the number and placement of end-screen elements, so verify the current layout before you render your final video.