Image Resizer
Resize images to exact pixel dimensions, with optional aspect-ratio lock.
Use ToolFit any image to 1280 × 720 (16:9) for video thumbnails.
The image is scaled onto a 1280 × 720 canvas, either cropping to fill the frame or fitting it with background bars, then exported as JPEG. YouTube's help pages recommend 1280 × 720 and a file under 2 MB; the tool warns you if the result is larger. SmartToolHub is not affiliated with YouTube.