Bounce rate measures single-page sessions where no further interaction (click, scroll, form submission) occurred before the user left. In Google Analytics 4, the concept was replaced by engagement rate — the inverse metric counting sessions where users did interact.

Why it matters: A high bounce rate can signal a mismatch between what users expected to find and what they saw. For content pages, a high bounce may be acceptable (the user found their answer). For landing pages, it typically indicates friction — slow load time, irrelevant content, or a poor mobile experience.

Quick tips:

Diagnose, don't just react: pair bounce rate with session duration and scroll depth to understand intent.
Improving Core Web Vitals — especially LCP — measurably reduces bounce on slow pages.
Ensure above-the-fold content matches the ad copy or organic search title that brought users in.