To learn more about the active campaign limits when using UCD Segments, contact the Insider One team, as limits may vary.
Some data used for segmenting users in web campaigns is stored via Local Storage and is not available in the Unified Customer Database (UCD). As a result, the segments available through browser-based methods and UCD may differ.
To ensure flexibility, Web Templates and Onsite Experiment campaigns offer a dual segmentation method. This allows you to choose whether to segment using browser-based data or UCD segments. That’s why the segment selection screen for these campaigns may look different from that of other campaign types.
Choose Segmentation Method
When you land on the Segment step, you will see the UCD segment by default. You can select any segment based on your campaign needs.

The available segment options are:
If you want to use some of the Browser-Based segments, click the Use Browser-Based Segments button. However, you cannot merge UCD segments and Browser-Based segments within the same campaign; instead, you must use either UCD segments or Browser-Based segments. For this reason, the previously selected segments are automatically cleared in the event of a segment type switch.

This means you can use the full capacity of UCD Segments or Browser-Based segment. However, you cannot use segment users on web campaigns based on data from UCD and local storage simultaneously.
Understanding Segment Logic and Access
Campaigns become visible after the second initialization of the Insider Tag in each session, once you land on the website. During the first initialization, the necessary data is retrieved from UCD to determine user eligibility
Available user segments are evaluated at the start of each session. In other words, any actions taken during the session will not affect the user's segment in real time.
A session is considered ended when the user either closes the browser/tab.
A session is considered ended when the user remains inactive on the website for 30 minutes or more.