How does Google Analytics track session expiration?

@jamison 

Google Analytics tracks session expiration by using a combination of browser cookies and timestamps.

When a user visits a website with Google Analytics tracking code installed, a unique ID is generated for the user and stored in a browser cookie. This ID is used to associate all subsequent actions taken by the user on the website with a particular session.

A session is defined as a period of user activity on a website, which can include multiple pageviews, interactions with forms and buttons, and other types of events. Google Analytics uses a timestamp to calculate the duration of each session, and sets a default session timeout of 30 minutes.

If a user is inactive for 30 minutes or more, or if they close their browser, the session is considered to have ended, and a new session will be started the next time the user visits the website.

However, it's important to note that session expiration and timeout settings can be customized in Google Analytics. Website owners can adjust the timeout settings to better match the typical behavior of their website users and ensure accurate tracking of user behavior.

@jamison 

To provide more accurate tracking, Google Analytics also uses additional techniques to handle situations where cookies may not be available or when a user switches devices.

One technique is called "engagement time", which uses a combination of JavaScript and server-side scripts to track user activity and calculate session duration. Engagement time measures the time a user spends actively engaged with a page, even if they are not actively clicking or scrolling.

Another technique is called "campaign timeout". When a user arrives at a website through a campaign, such as a Google AdWords click, a campaign timeout is set. This timeout ensures that if a user leaves the website and then returns within a specified period (usually 30 minutes), the session will still be attributed to the original campaign.

It's worth mentioning that while Google Analytics tries to accurately track session expiration, it is not always perfect. Some users may have browser settings that prevent cookies from being stored or cleared, which can impact session tracking. Additionally, if a user has JavaScript disabled, certain tracking methods may not be effective.

Overall, Google Analytics uses a combination of cookies, timestamps, engagement time, and campaign timeouts to track session expiration, aiming to provide accurate data on user behavior on websites.

@jamison 

You're close, but I wanted to provide a slight correction. Google Analytics does not use engagement time as a separate technique to track session expiration. Instead, engagement time is used to calculate the time a user spends actively engaged with a page during a session. It is not directly related to session expiration.

Additionally, Google Analytics primarily relies on browser cookies to track session expiration. When a user visits a website, a cookie containing a unique ID is set in their browser. This ID is used to associate all subsequent actions during the session with a particular user.

The default session timeout in Google Analytics is 30 minutes of inactivity. If a user does not perform any action on the website within this timeframe, the session will end. However, it's important to note that the session timeout can be customized in the Google Analytics settings.

In some cases where cookies may not be available or if a user switches devices, Google Analytics can use techniques like cross-device tracking and user identification to maintain session continuity. For example, if a user starts a session on their mobile device and later switches to their desktop computer, Google Analytics can link both sessions together and attribute them to the same user.

Overall, Google Analytics primarily tracks session expiration using browser cookies and applies various techniques to ensure accurate tracking, including customization options for session timeout settings.