If you notice that the processor is getting hotter or is slowing down while browsing the web with Chrome, this could be due to ads that are eating up resources.

You can now prevent this with turning on a setting in Chrome.

Heavy Ad criteria

An ad is considered heavy if the user has not interacted with it (for example, has not tapped or clicked it) and it meets any of the following criteria:

  • Uses the main thread for more than 60 seconds in total
  • Uses the main thread for more than 15 seconds in any 30 second window
  • Uses more than 4 megabytes of network bandwidth

All resources used by any descendant iframes of the ad frame count against the limits for intervening on that ad. It’s important to note that the main thread time limits are not the same as elapsed time since loading the ad. The limits are on how long the CPU takes to execute the ad’s code.

Testing the intervention

You can test the new intervention in Chrome 84 and upwards.

  • Enable chrome://flags/#enable-heavy-ad-intervention
  • Disable chrome://flags/#heavy-ad-privacy-mitigations

Setting chrome://flags/#enable-heavy-ad-intervention to Enabled activates the new behavior, but by default there is some noise and variability added to the thresholds to protect user privacy. Setting chrome://flags/#heavy-ad-privacy-mitigations to Disabled prevents this, meaning the restrictions are applied deterministically, purely according to the limits. This should make debugging and testing easier.

By Harry