There are 6 total thumbnails that an image can be resized to. Each one is accessable by appending a single character suffix to the end of the image ID, and before the file extension.
For example, the image located at http://i.imgur.com/12345.jpg has the Medium Thumbnail located at http://i.imgur.com/12345m.jpg
The thumbnails are:
s = Small Square (90x90)...
Had you said previews on the progress bar (or even had uploaded images) I might not have misunderstood first time around. IF that is what you mean:
The progress bar preview works on some videos and doesn't work on others. There is no explanation for it, nor can you fix it.
from YouTube Help Forum might be of interest (though I'm not convinced correct).
As this feature is available to all accounts, you are missing something but we can't tell you exactly what: some Google Editors1 features:
are only available in Chrome.
requires to be signed in a Google Account
requires a G Suite account
Please bear in mind that you could send your feedback directly to Google through Google Feedback 2
Got it! I tried this from RayB, and it helped: https://webapps.stackexchange.com/a/140932
went to my test channel
posted the Google Doc link
chose "delete file from Slack" from its menu
reposted the link
Voilà! it posted with the new title and thumbnail
Yes, it is possible. After you upload/submit the video you can choose autogenerated thumbnail images for your video:
or you can set your own image after your account gets verified:
The verification process looks like this:
If the video is not yours you can still do it by editing the embed code - for example:
official embed code:
<iframe width="560" ...
There is a inbuilt functionality called featured images in WordPress:
Reference : http://en.support.wordpress.com/featured-images/
I am not sure whether it will be displayed in Facebook Embed Post but it is worth giving a try if you do not already have.
See the below reference: