Surveys have been used as main tool of data collection in many areas of research and for many years. However, the environment is changing increasingly quickly, creating new challenges and opportunities. This article argues that, in this new context, human memory limitations lead to inaccurate results when using surveys in order to study objective online behavior: People cannot recall everything they did. It therefore investigates the possibility of using, in addition to survey data, passive data from a tracking application (called a "meter") installed on participants’ devices to register their online behavior. After evaluating the extent of some of the main drawbacks linked to passive data collection with a case study (Netquest metered panel in Spain), this article shows that the data from the web survey and the meter lead to very different results about the online behavior of the same sample of respondents, showing the need to combine several sources of data collection in the future.