Nowadays, website owners, advertisers, and data vendors can draw on a variety of techniques to track users on the Web. Here, the tracking range can vary from single websites to long-term browsing sessions across several websites and devices. Even though they are widely used, most of these techniques have in common that they are not familiar to average and even web-minded users. Therefore, most users are not able to realize the magnitude of web tracking and its consequences, not to mention to resist tracking. In times of rising concerns about data protection and privacy, this paper is intended to illustrate how web tracking works and which standard techniques are commonly used. The paper also provides an outlook on promising new tracking techniques based on behavioral biometrics. Furthermore, since browser forensics is already a subject to digital investigations, the usefulness of tracking techniques for forensic purposes and their applicability in light of the principle of proportionality is discussed. Finally, possible countermeasures and their effectiveness are indicated.