How to use it
- Press Choose image, drag a file onto the box or paste an image. It stays in your browser; nothing is uploaded.
- Type the video title and channel name, and the length for the time badge.
- Switch between Home feed, Search, Sidebar and Phone, and between light and dark.
- Use Add a version to load up to three thumbnails and see them next to each other.
What to look for
The small size first. In the sidebar view a thumbnail is only about 170 pixels wide. If you can't read the text there, it's too small or too long.
Both themes. A dark thumbnail that pops on a white page can disappear in dark mode, and the other way round.
The bottom-right corner. The time badge covers it. Keep faces and words away from it.
Title and picture together. Feeds cut titles after about two lines. The thumbnail should add something the title doesn't say, not repeat it.
Neutral neighbours
The other cards in the preview are plain grey placeholders, not real videos. That's deliberate: your thumbnail has to stand out on contrast and clarity alone, without being compared to someone else's work.
Testing for real
A preview tells you whether a thumbnail is readable. Whether it gets clicks is a different question: YouTube Studio can test up to three titles and thumbnails on real viewers and keeps the one with the most watch time (on a computer, for eligible long-form videos).
Questions
- Is my thumbnail uploaded anywhere?
- No. The image is read by your browser and drawn on the page. Close the tab and it's gone.
- Does it look exactly like YouTube?
- It's a close approximation of the layout at the time of the last check, not a copy. YouTube changes its design often, so treat sizes as a guide.
- What file should I test?
- The file you plan to upload: 16:9, at least 1280×720 if you can, as JPG or PNG. YouTube's limit is 2 MB from a phone and 50 MB from a computer.