Unique Visit

Unique visit, also known as single attendance, is metric used in internet marketing to describe a unit of traffic, which is further used to estimate a website's true audience size. Unique visits are usually measured over a given time frame.

There are several methods to calculate unique visits. Most common include differentiation by a user IP address or cookie tracking. Neither of the methods is 100% accurate, due to such factors as cookie-disabled browsers, proxy servers or dynamic IP assignment. Nonetheless it is possible to provide a workable estimate (or an educated guess) of the audience size using these methods.

The data to calculate the metric can come from log files stored on an http server or from user browsers. There are advantages to both methods. Log files always include the data left by spiders (or programs used to collect data from websites) and is occasionally useful. Using javascript to collect information from user browsers on the other hand can provide additional parameters, such as browser make and model, user screen resolution and operating system, making the metric more valuable in some aspects.