yes, according to their documentation it is.
https://help.vimeo.com/hc/en-us/articles/115004485728-Autoplaying-and-looping-embedded-videos
EDIT:
Advance browsers like FireFox, Chrome and Safari are now blocking video autoplay by default.
CHROME Auto-Play Policy:
https://developers.google.com/web/updates/2017/09/autoplay-policy-changes
The Media Engagement Index, or MEI for short, a way of Chrome is to allow AutoPlay audio on your page to be based on your previous interactions with this webpage as a user. You can see what this looks like by going to
chrome://media-engagement/
MEI is calculated per user profile, and is persisted to incognito mode.

WEBKIT/SAFARI Auto-Play Policy:
https://webkit.org/blog/7734/auto-play-policy-changes-for-macos/
FIREFOX Auto-Play Improvements:
https://www.ghacks.net/2018/09/21/firefox-improved-autoplay-blocking/
NOTE:
Don’t assume a media element will play, and don’t show the pause button from the start. Look at the Promise returned by the play function on HTMLMediaElement to see if it was rejected:
var promise = document.querySelector('video').play();
if (promise !== undefined) {
promise.catch(error => {
// Auto-play was prevented
// Show a UI element to let the user manually start playback
}).then(() => {
// Auto-play started
});
}