To download a YouTube HD thumbnail, you can follow these steps:


1. Go to the YouTube video for which you want to download the HD thumbnail.

2. Pause the video at the desired frame for the thumbnail.

3. Right-click on the video and select "Copy video URL" or "Copy video URL at current time."

4. Open a web browser and paste the copied URL into the address bar.

5. Modify the URL by replacing "youtube.com" with "img.youtube.com/vi" and add "/maxresdefault.jpg" at the end.

   For example, if the original URL is: 

   `https://www.youtube.com/watch?v=ABC123`

   Replace it with:

   `https://img.youtube.com/vi/ABC123/maxresdefault.jpg`

6. Press Enter or Go to load the modified URL.

7. The HD thumbnail image will be displayed in your web browser.

8. Right-click on the thumbnail image and select "Save image as" or "Save picture as" to save it to your desired location on your computer.


Please note that not all YouTube videos have a high-resolution thumbnail available, so this method may not work for every video. Additionally, be sure to respect the copyright and usage rights of the thumbnail image, especially if you plan to use it for any public purposes.