Using YouTube thumbnails in blog posts and presentations
Thumbnails are handy for roundups, reviews and slides about a video, but they belong to someone else, so use them carefully.
Good practice is to show a thumbnail only to illustrate a video you are actually discussing, link to the original video and name the channel. When you can, embed the video instead of copying the image. Add alt text such as “Thumbnail of [video title] by [channel]”.
Avoid using someone’s thumbnail to promote an unrelated product, to suggest endorsement or as your own artwork. For commercial use, ask the creator first. This is general guidance, not legal advice.