MyThumbTester guide
Which YouTube links can you paste into a thumbnail downloader?
See the exact public YouTube URL shapes and raw video ID that MyThumbTester accepts before it checks available thumbnail images.
Paste a public video link or a raw 11-character video ID
MyThumbTester accepts a public YouTube watch URL, Shorts URL, embed URL, live URL, youtu.be short link, mobile or Music watch URL, or a raw 11-character video ID. Its browser-side parser reads the video ID only from those supported shapes, then checks five public thumbnail image names for that one ID. A valid-looking link that does not contain a supported public video ID is rejected before any thumbnail image request is made. This is a reproducible behavior of the implemented parser, not a prediction of click-through rate, ranking, distribution, or views.
The practical check is simple: paste one link, submit it, and look for the available-size results. If the form reports that it needs a public watch, Shorts, embed, live, or youtu.be URL—or an 11-character ID—copy the public video link again rather than guessing a thumbnail URL.
Supported link shapes map to the same video ID
For a standard watch page, the parser reads the v parameter. For youtu.be, it reads the first path segment. For Shorts, embed, and live pages, it reads the second path segment after the type. The parser also permits the youtube.com, m.youtube.com, and music.youtube.com hosts for watch links, and it accepts a bare ID only when it contains exactly 11 letters, digits, underscores, or hyphens.
This means the downloader is checking a single public video ID, rather than treating each shared link shape as a separate kind of image. A playlist link, channel page, unsupported path, malformed URL, or non-public video reference does not provide the single ID that this workflow requires.
After the input is accepted, choose only a size that loads
An accepted link is only the first step. MyThumbTester next tries maxresdefault, sddefault, hqdefault, mqdefault, and default, then lists only image responses that load with usable browser-read dimensions. Available sizes vary by video, so an accepted link does not promise a maximum-resolution image.
Choose one listed public image to download as a JPG or open it in the six-layout thumbnail tester. The downloader handles public thumbnail images only; it does not download the video, access private material, or make an unavailable image appear.
What an accepted link cannot tell you
A successfully parsed link cannot confirm image ownership, reuse rights, future availability, or how YouTube will display the image in every surface. It also cannot show which title or thumbnail will earn more clicks, rankings, distribution, or views. Use the parser and layouts for a concrete public-image review, then use real platform data for performance questions.