Session

A session is a group of interactions that a single user has with a website within a bounded time period. It begins when the user arrives at the site and ends when they leave or when a period of inactivity expires — Google Analytics uses a 30-minute inactivity timeout by default. If a visitor reads an article, leaves for 45 minutes, and returns, that counts as two sessions.

A session is the container that holds pageviews and other interactions (clicks, form submissions, video plays). One session may contain one pageview (the visitor arrived, read one page, and left — a bounce) or many (the visitor browsed several articles, checked the about page, and signed up for a newsletter). The number of pageviews per session — pages per session or page depth — is a key engagement metric because it directly multiplies ad revenue: more pages viewed per visit means more ad impressions served from the same session.

Sessions are the denominator in several important metrics. Session RPM (revenue per 1,000 sessions) is often more useful than page-level RPM because it captures the full revenue generated by a visit, including revenue from multiple pages. If a site earns $8 per 1,000 pageviews and averages 2 pages per session, its session RPM is$16 — the actual revenue per visit. Premium ad networks like Mediavine report session RPM as the primary performance metric because it aligns with the publisher’s real unit of attention: the visit.

The distinction between sessions and unique visitors matters for understanding audience size versus engagement. A site with 100,000 sessions per month might have 70,000 unique visitors — meaning some visitors came more than once. For subscription-based monetization, unique visitors are the relevant number (each person is one potential subscriber). For advertising, sessions are the relevant number (each visit generates ad revenue regardless of whether the visitor has come before).

Session definitions have grown more complicated with modern browsing patterns. Users open tabs and return to them hours later. Mobile users switch between apps, backgrounding the browser. Single-page applications never trigger a traditional page load. Analytics platforms handle these cases differently, which means session counts are not directly comparable across tools or across sites using different configurations.

Related terms

• Pageview — the individual page loads that sessions contain
• Bounce rate — the proportion of sessions with only one pageview
• Revenue per mille — the revenue metric that can use sessions as the denominator
• Conversion rate — often calculated per session rather than per pageview