Every YouTube video has a predictable thumbnail URL structure. If you know the video ID, you can construct any thumbnail URL manually.
The URL Pattern
YouTube serves thumbnails from img.youtube.com using this pattern:
https://img.youtube.com/vi/{VIDEO_ID}/{FILENAME}
Where {VIDEO_ID} is the 11-character ID from the YouTube URL (e.g., dQw4w9WgXcQ) and {FILENAME} is one of:
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How to Find the Video ID
The video ID is the 11-character string after v= in a YouTube URL:
https://www.youtube.com/watch?v=dQw4w9WgXcQ
For short links, it's the part after youtu.be/:
https://youtu.be/dQw4w9WgXcQ
Use Tube Fetch for Instant Access
Rather than constructing URLs manually, Tube Fetch extracts the video ID automatically and generates all five thumbnail URLs for you in one click.