YouTube channels often use custom thumbnails for their videos, many of which are examples of the "YouTube Face" phenomenon. YouTube may soon have a compelling alternative for creators, though. The site is running a quick experiment with auto-generated thumbnails. If you're suddenly seeing different video previews, that might be why.

According to YouTube, 0.3% of users are now seeing auto-generated video thumbnails across the entire site in place of custom thumbnails. The image YouTube currently uses for this is the second suggested image when videos are uploaded. The remaining 99.7% of YouTube users still see whatever thumbnail the uploader has chosen.

YouTube says it's not phasing out custom thumbnails, but it intends to improve the auto-generated thumbnails used on most videos. Presumably, it wants to see how different previews affect clicks. If the automated options get better, maybe more creators will use them in place of custom thumbnails. YouTube calls this a "brief" experiment, but that could mean a lot of things.