3. Poster

The poster attribute (poster="#") should always be supplied with the <video> element. This attribute takes a URL as its value, which should point to an image that is displayed in place of the video until the visitor elects play the video.

Single-Source

Element Breakdown
<video src="#" poster="#" width="" height="" preload controls></video>

Multiple-Source

Element Breakdown
<video poster="#" width="" height="" preload controls>
   <source src="#" type="">
   <source src="#" type="">
</video>

Note The image should be the same width/height ratio as the video element. Image of matching video and video poster sizes


html attribute image video