Videos not autoplaying in Safari in 10.12
There is a hidden setting in Safari that disables auto-playback of videos.

To enable auto-playback, paste the commands below in Terminal.app (CMD+Space, type "Terminal"). Quit Safari first.

defaults write com.apple.Safari WebKitMediaPlaybackAllowsInline -bool true
defaults write com.apple.SafariTechnologyPreview WebKitMediaPlaybackAllowsInline -bool true
defaults write com.apple.Safari com.apple.Safari.ContentPageGroupIdentifier.WebKit2AllowsInlineMediaPlayback -bool true
defaults write com.apple.SafariTechnologyPreview com.apple.Safari.ContentPageGroupIdentifier.WebKit2AllowsInlineMediaPlayback -bool true


You may need to reboot your Mac.

To disable auto-playback in Safari use the commands below:

defaults write com.apple.Safari WebKitMediaPlaybackAllowsInline -bool false
defaults write com.apple.SafariTechnologyPreview WebKitMediaPlaybackAllowsInline -bool false
defaults write com.apple.Safari com.apple.Safari.ContentPageGroupIdentifier.WebKit2AllowsInlineMediaPlayback -bool false
defaults write com.apple.SafariTechnologyPreview com.apple.Safari.ContentPageGroupIdentifier.WebKit2AllowsInlineMediaPlayback -bool false


In case this should not work, please let us know if the video-playback works with the Safari Technology Preview.