Google Chrome collects site engagement metrics, and Chromium project documentation explains exactly what they are and how they are used.
Site Engagement Metrics
The documentation for the Site Engagement Metrics shares that typing the following into the browser address bar exposes the metrics:
chrome://site-engagement/
What shows up is a list of sites that the browser has visited and Site Engagement Metrics.
Site Engagement Metrics
The Site Engagement Metrics documentation explains that the metrics measure user engagement with a site and that the primary factor used is active time spent. It also offers examples of other signals that may contribute to the measurement.
This is what documentation says:
“The Site Engagement Service provides information about how engaged a user is with a site. The primary signal is the amount of active time the user spends on the site but various other signals may be incorporated (e.g whether a site is added to the homescreen).”
It also shares the following properties of the Chrome Site Engagement Scores:
The score is a double from 0-100. The highest number in the range represents a site the user engages with heavily, and the lowest number represents zero engagement.
Scores are keyed by origin.
Activity on a site increases its score, up to some maximum amount per day.
After a period of inactivity the score will start to decay.
What Chrome Site Engagement Scores Are Used For
Google is transparent about the Chrome Site Engagement metrics because the Chromium Project is open source. The documentation explicitly outlines what the site engagement metrics are, the signals used, how they are calculated, and their intended purposes. There is no ambiguity about their function or use. It’s all laid out in detail.
There are three main uses for the site engagement scores and all three are explicitly for improving the user experience within Chromium-based browsers.
Site engagement metrics are used internally by the browser for these three purposes:
Prioritize Resources: Allocate resources like storage or background sync to sites with higher engagement.
Enable Features: Determine thresholds for enabling specific browser features (e.g., app banners, autoplay).
Sort Sites: Organize lists, such as the most-used sites on the New Tab Page or which tabs to discard when memory is low, based on engagement levels.
The documentation states that the engagement scores were specifically designed for the above three use cases.
Prioritize Resources
Google’s documentation explains that Chrome allocates resources (such as storage space) to websites based on their site engagement levels. Sites with higher user engagement scores are given a greater share of these resources within their browser. The purpose is so that the browser prioritizes sites that are more important or frequently used by the user.
This is what the documentation says:
“Allocating resources based on the proportion of overall engagement a site has (e.g storage, background sync)”
Takeaway: One of the reasons for the site engagement score is to prioritize resources to improve the browser user experience.
Role Of Engagement Metrics For Enabling Features
This part of the documentation explains that Chromium uses site engagement scores to determine whether certain browser features are enabled for a website. Examples of features are app banners and video autoplay.
The site engagement metrics are used to determine whether to let videos autoplay on a given site, if the site is above a specific threshold of engagement. This improves the user experience by preventing annoying video autoplay on sites that have low engagement scores.
This is what the documentation states:
“Setting engagement cutoff points for features (e.g app banner, video autoplay, window.alert())”
Takeaway: The site engagement metrics play a role in determining whether certain features like video autoplay are enabled. The purpose of this metric is to improve the browser user experience.
Sort Sites
The document explicitly says that site engagement scores are used to rank sites for browser functions like tab discarding (when memory is tight) or creating lists of the most-used sites on the New Tab Page (NTP).