Thumbnail

Thumbnails are a way of advertising videos which can lead viewers to ultimately click on it, and watch the video. They are pictures that appear on the video preview screen on the YouTube page.
Hovering the cursor over them in desktop will render a small preview of the video. Looking at a video on the homepage in mobile will also render a preview of the whole video. Custom thumbnails were added in the year 2009.
The thumbnail of a video is supposed to describe the video and its content. However, over time, some YouTubers have manipulated the use of these and started to deceptively advertise their videos, also known as clickbait.
== Details ==
=== Requirements ===
To be eligible to upload and apply a custom thumbnail, one must be eligible of the intermediate features level on their YouTube account. To reach the intermediate feature eligibility, a phone number must be verified by receiving a code from YouTube via SMS in the URL: youtube.com/verify. Otherwise, they are given three images from their video to choose from.
=== Size and resolution ===
YouTube has placed some recommendations for custom thumbnails as follows:
* The optimal size for a YouTube thumbnail is 1280px by 720px with a minimum width of 640px.
* The preferred aspect ratio is 16:9. Using a different aspect ratio will force YouTube to resize the thumbnail and may introduce .
* The maximum file size for normal video thumbnails is 2 megabytes before being compressed, and 10 megabytes for podcast video thumbnails before being compressed.
* The allowed image format for thumbnails are JPG, GIF, or PNG.
** YouTube doesn't allow animated GIFs or PNGs, and will use the first frame of the animation as the thumbnail instead.
** YouTube doesn't support transparency in thumbnails, trying to upload a partially-transparent PNG will result in the alpha channel mixing with the black background in YouTube's preprocessing. Transparency in GIFs will result in black being used in place of the transparent pixels.
=== Thumbnail policy ===
All thumbnails must follow the YouTube Community Guidelines. Failure to do so will risk the YouTuber to be in a 30 day restriction of using custom thumbnails, or banned from using custom thumbnails entirely.
When a video is caught using a thumbnail that violates the Community Guidelines, the custom thumbnail may be replaced by YouTube's auto-generated thumbnails.
== Trivia ==
* It is unknown if the three suggested auto-generated thumbnails by YouTube in the Studio are purely randomly selected frames from the video, or if there are heuristics behind it.
== References ==
Category:History of YouTube
Category:YouTube