Web analytics, or metrics, are measures of behavior of website users that are automatically collected across entire visitor populations or large samples. Data such as the number of visitors to a website, where they are from, which pages they view, and which links they click, can be measured, collected, analyzed and reported. Web analytics are relevant to usability practitioners in that they can provide insight into the large-scale behavior of website users to understand and improve (optimize) the website.
Web analytics cannot provide answers to questions about user motivations or underlying needs and goals. Web analytics may indicate that users are abandoning a checkout process at a particular point, but they cannot be used to explain why this is happening. Usability testing of the issues that are found through web analytics brings the deeper understanding needed to fix these usability problems. Additionally, in-person observations of users can lead to insight that informs what metrics are worthwhile to collect, and how to interpret them.