Resize images for YouTube

Thumbnails have a file size ceiling

Custom thumbnails are limited to 2 MB, and a 1280 × 720 JPEG comfortably fits — unless it has been exported at maximum quality from a design tool. If an upload is rejected, drop the quality to around 80 and the file will typically land under 400 KB with no visible difference at thumbnail scale.

Use JPEG rather than PNG for photographic thumbnails. A PNG of the same image is often five times larger for no visible benefit once it is displayed at 320 pixels wide in a sidebar.

Design for the small version

A thumbnail is authored at 1280 × 720 and seen at a fraction of that. Anything that reads only at full size — thin outlines, small captions, busy backgrounds — disappears in the feed. Check your batch at around 20 percent before committing to a style.

Channel banners and the safe area

The banner is uploaded at 2560 × 1440 but displayed very differently on television, desktop and mobile. Only a central region is guaranteed visible everywhere, so keep names and logos well within the middle of the image rather than filling the full canvas.

Consistency across a channel

Thumbnails are seen in a column of competing thumbnails, so a channel that uses one framing, one type treatment and one colour approach is recognisable before the title is read. That consistency is a batch problem rather than a design problem: the same crop, the same dimensions, the same export settings every time.

Processing a set of stills in one pass — identical dimensions, identical quality, sequential names tied to the video — is what keeps a back catalogue coherent. It also makes updating a thumbnail later trivial, because the source frames are already named in a way that says which video they belong to.