Chrome JavaScript throttling experiment improves Battery significantly

[harlan4096]

Web browsers uses a lot of battery when they are run on mobile devices such as laptops. While it helps to use content blockers and other extensions to remove or block elements that may draw additional power, it is still problematic from a user perspective.

Google has run experiments in the past couple of months in its Chrome web browser to find out if the throttling of JavaScript in background tabs has an effect on the battery usage of the web browser.

Chromium engineers decided to analyze "the work done by popular sites in the background" and determined that "a lot of work was done from JavaScript timers"at were not "valuable to the user" often.

The idea was born to reduce the number of wake ups from JavaScript timers in background tabs in the web browser to find out if that would improve battery life.
Currently, JavaScript wake ups are limited to 1 wake up per second in stable versions of the Chrome web browser.

Google ran several experiments to determine if the throttling of JavaScript wake ups would improve battery life. Here are the results:

Experiment 1: 36 popular sites in background tabs, about:blank in foreground.

• Current status: Median time to discharge 6.4 hours
  
• Throttled status: Median time to discharge 8.2 hours
  

Experiment 2: 36 background tabs, YouTube in foreground

• Current status: Median time to discharge 4.7 hours
  
• Throttled status: Median time to discharge 5.3 hours
  

A new Chrome experimental flag is available to enable the feature in development versions of the Chrome we browser (Canary).

• Name: Throttle Javascript timers in background.
  
• Description: When enabled, wake ups from DOM Timers are limited to 1 per minute in a page that has been hidden for 5 minutes.
  

Here is how to enable the experiment:

1. Load chrome://flags in the web browser's address bar.
   
2. Search for Throttle Javascript timers in background.
   
3. Set the flag to Enabled.
   
4. Restart the browser.
   

Google Chrome will limit JavaScript timers of background pages after the restart automatically; this is applied to pages that have been in the background for at least five minutes.

The feature may be introduced in Chrome 86 on the desktop (currently Canary).

Google plans to introduce an Enterprise policy to disable the intervention. The idea behind the policy is to provide administrators with an option to turn the functionality off if they notice that it breaks functionality.

Tests will be run to find out if the feature will break certain features on sites.

Other Chromium-based browsers such as Microsoft Edge, Brave, Vivaldi, or Opera, will get the feature as well unless the developers of the browsers deactivate it actively. It is very likely that Mozilla will implement this also in the Firefox web browser in the future.

Battery life improvements are always welcome, especially if a small change extends the battery life by a lot.

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