Google said this week that Chrome 66 now blocks "about half" of the videos that feature auto-playing sound. Engineers added this feature in Chrome 66, released in mid-April.
The browser maker says Chrome uses a list of 1,000 sites for which it allows videos to play with sound at page load. Most of these are reputable sites such as YouTube, Vimeo, DailyMotion, and others.
For the rest, Chrome prevents videos from playing sound, and the user must specifically press the play button or interact with the video before the browser would allow any audio to play.
Further, as users browse the web using Chrome and allow videos to play, the browser also learns in the background on which sites the user likes to watch videos and adds them to the default whitelist of 1,000 sites. Similarly, if the user blocks sites from playing audio, those sites are removed from the whitelist.
"That list changes as Chrome learns and enables autoplay on sites where you play media with sound during most of your visits, and disables it on sites where you don’t," said John Pallett
Product Manager for Google Chrome. "This way, Chrome gives you a personalized, predictable browsing experience."
Pallett now suggests, citing Chrome 66 telemetry, that about a half of the sites that autoplay videos are doing it without permission or the user expecting to hear sound.
Chrome engineers started working on this feature last year, in September, as part of a larger plan to prevent websites from hassling users. Chrome 66 is the third stage of Google's fight against sites that play sounds without permission.
In Chrome 63, Google rolled out a system to let users mute sites forever. In Chrome 64, the browser started muting ads that attempted to play sounds at page load.