What is a poster image? In the event your video doesn’t play a poster image will show instead. If you don’t specify a poster image then the user will just see blank white space. A bad look

Why bother? Why would my video not play? 

1) Your video auto plays when viewed on a laptop or tablet. But not so on a phone. There are ways around that, but I don’t necessarily recommend them. Because your phone has good reasons for not auto playing video: to save battery power.

“Mobile browsers often block autoplay for videos with sound to save data and provide a better user experience.”

cheskakimCheska Sky Kim https://discourse.webflow.com/t/background-video-wont-start-autoplay/262624/5

2) When you do things on the web the right way google likes you. This is called SEO (search engine optimization). Having a poster image on your video increases you page speed load time on mobile. Because the the phone is not looking for a poster image that is not there. It sees the image you have designated and so the page loads quickly.

To show you what I mean I ran a page speed load time test for the big orange planet home page both before and after I added a poster image. I ran these tests on https://pagespeed.web.dev/

Before the page speed load time on mobile was 64. After I added the poster image the page speed load time was 77. That’s Impressive, and easy to do!

responsive design seo tutorial