Just follow these steps to download
Go to the youtube website or app, open the video you want to download thumbnails, click the "Share" icon at the bottom of the video, the video link will appear, click to copy the video URL.
Paste the video link into the thumbnail downloader search box, click the "grab" button, and the downloader will extract the video thumbnail image. This process is very fast and can complete in an instant.
Thumbnail downloader will extract thumbnails in four dimensions: MQ 320X180, HQ 480X360, SD 640X480, HD 1280X720.All the video thumbnails are in jpg format. 1280 pixels wide by 720 pixels high is used most often in YouTube players and previews. You can choose a size you want to download.
If you are on a computer, Right-click on the thumbnail, then select "Save Image As…" from the dropdown menu. Click the "Save" button. If you one the mobile, tap anywhere on the thumbnail picture and hold your finger down. An ‘options’ window will appear. From that list, select Save image.
It's best not to do this. All video thumbnails belong to YouTube creators, and you have no right to use them. On the other hand, the thumbnails of the videos you download are not necessarily related to your videos, and they are not very helpful for increasing YouTube views.
Yes, the process is the same as downloading youtube video thumbnails.
The two are equally important. The video title tells the viewer the content of the video, and the video thumbnail can increase the clicking of the video.
Video thumbnails are like book covers. Good covers can attract readers to view and buy books. Bad covers do not even have the opportunity to attract readers to pick up books. Similarly, good video thumbnails can entice viewers to click and watch your video, and possibly follow your video channel. But lousy video thumbnails don't even have the opportunity to attract viewers to click.
The youtube help center gives suggestions for video thumbnail sizes:
The Google Help Center clearly states:
To change the thumbnail of a video that has already uploaded, you should first log into YouTube Studio and follow these steps: