MP4 custom thumbnail instead of GIF

We recently made an update to allow for .mp4 videos as custom thumbnails for videos or any media item, instead of using gif files that can be large/download slow and be of lesser quality.

Some guidelines on how you should encode/size the .MP4 file:

• Export your .MP4 file for the Custom Thumbnail for a duration around 4 seconds, for a target file size under 4mb. 
  
  
• please encode your .MP4 file for Custom Thumbnail with streaming disabled in the encode
  
  
• export the .MP4 for Custom Thumbnail, at either 720x405px or 1280x720px dimension
  
  
• please remove any audio for the .MP4 file when encoding for the Custom Thumbnail

IMPORTANT:  Please remember that these .MP4 files are going to be used as thumbnails in a thumbnail-first gallery so the larger the .MP4 file size and the more .MP4 custom thumbnails in a gallery, there will be more degradation in page speed for your visitors and navigating in your own Media Library can become slower.

Steps to do this are listed below:

 1. Find the media item you want to upload a video thumbnail for. You can either double click on it or select it and hit edit:

 2. you should then see the panel below with the custom thumbnail upload section:

 We've provided a video below on the entire process: