Google is continuing to work to crack down on autoplaying video around the Web. On the one hand, having a new tab unexpectedly start squawking and making a racket is tremendously annoying. But on the other hand, we visit sites like YouTube explicitly to watch video and probably want those videos to play as soon as the page loads. Chrome 66, due for release in mid-April, will include a new heuristic system that will attempt to block noisy autoplaying video when it's unwanted while still permitting it on sites like YouTube and Netflix where the video is the entire purpose of the site.

Under the new policy, Google is defining four classes of video that will be allowed to autoplay. The first three categories are fairly straightforward. Silent videos with no audio content at all will always be allowed to autoplay. If a user interacts with a site (an action that includes tapping or clicking on a site, not merely scrolling on it), the site will be able to autoplay video during that browser session. Sites that are pinned to the Android home screen are also allowed to autoplay.

The fourth category is more complex. In the desktop browser, sites that are frequently used for media playback will be allowed to autoplay video, provided that the video meets certain criteria. Chrome will track each visit to such sites and make a record of interaction to play the video. To qualify for autoplaying, a user must have elected to play "significant" video on the site on at least 30 percent of their visits, tracked across 20 site visits. If over time the number of video playbacks drops to below 20 percent, autoplay will be disabled on the site. Video is only deemed to be "significant" if it's larger than 200×140, is longer than 7 seconds, has an audio track, isn't muted, and is on a visible tab.

Update: the article previously described Google's documented limits as five visits, 70 percent to enable autoplay, and 50 percent to disable it again. It now describes the limits as actually implemented in Chrome, which are different from those in the documents.

Google says that the categorization of a site should roam as part of your user profile, so if a site meets the autoplay threshold on one device, it will meet the threshold on all your devices.

The company's expectation and intent behind the system is that only those sites dedicated to video content are likely to meet the autoplay criteria. News sites that have mixed content, however, are unlikely to see enough video activations to reach the level required. As such, those sites will require a manual interaction to play videos every time.