YouTube thumbnail sizes and URLs
YouTube serves every video's thumbnails as public images on its image server, i.ytimg.com, at a predictable address: https://i.ytimg.com/vi/ followed by the video ID and a file name. This tool builds those addresses for you and loads the images straight from YouTube in your browser, without going through Vidfora's servers.
- maxresdefault.jpg: 1280 x 720, 16:9
- sddefault.jpg: 640 x 480, 4:3
- hqdefault.jpg: 480 x 360, 4:3
- mqdefault.jpg: 320 x 180, 16:9
- default.jpg: 120 x 90, 4:3
- oar2.jpg: the portrait image for Shorts
Why some sizes have black bars
The 640 x 480, 480 x 360 and 120 x 90 files are 4:3. When the thumbnail is 16:9, the aspect ratio YouTube recommends for videos, YouTube fits it inside the 4:3 frame with black bars above and below. If you want the image without bars, use maxresdefault or mqdefault, which are both 16:9.
Why is the max-resolution thumbnail missing?
YouTube doesn't have every size for every video. When a file doesn't exist, YouTube answers with an error or a small gray placeholder image, and this tool labels that size 'Not generated for this video' instead of letting you download a blank image. The smaller sizes are usually still there.
Even maxresdefault isn't necessarily the file the creator uploaded. YouTube now recommends uploading thumbnails at 3840 x 2160, but the largest public version it serves is 1280 x 720.