Targeting Registered Users
When doing targeted releases you may already know very well who your user is. In these cases you might be interested in releasing a feature to a subset of users only so that you can gather feedback and re-iterate on your feature. ProbeBeta™ default category for probes is for Registered Users.
Identifying these users can be easily done by using a user ID that you also use internally which can be numeric or a string user ID. These user IDs could be your beta users who are early adopters of your feature. You can import these user IDs using ProbeBeta™ to Beta Users segment. Alternatively, you can update Beta Users segment via RESTful APIs so that your segment is always up to date.
ProbeBeta™ also allows multiple attributes to be used as an identifier. For example, you might be interested in rolling out a feature to registered users who are on free tier and have opted in to a newsletter. ProbeBeta™ does not have a limitation to number of attributes that you use to define your target audience. Using ProbeBeta™ Console you can easily define the logic in any way you like using comparison and logical operators without any coding.

Targeting Anonymous Users
If you are trying to target users who are just passing by but have not registered to any of your products it is still possible to target them. We can use their IP address and browser details to uniquely identify them.
ProbeBeta™ is able to using their IP address to determine their geographical location. This allows you to roll out features region by region until you are satisfied with the results and want to roll it out to all your users.
Just like with Registered Users ProbeBeta™ makes the best effort to make sure that your users are having a consistent user experience. Once a feature has been turned on for a user it will remain turned on for that IP address until a kill switch is used for this probe.