What's the difference between event scope and session scope?

Event scope describes one hit. Session scope describes the whole visit.

Every custom property in Feasible is one or the other, and you pick when you enable it. This looks like a detail and it isn’t - the scope decides the denominator of every conversion rate you read off that property.

Event scope is for things that are true of a single action. The plan a purchase was on. The search_term on a search. The url of an outbound click. It varies hit to hit within one visit, and it should.

Session scope is for things that are true of the person for the whole sitting. Whether they were logged in. Their account tier. Which A/B variant they landed in. It’s set once and applies to everything they do.

Here’s why it matters. Say you tag a property logged_in and want the conversion rate for logged-in visitors.

• Session-scoped, the denominator is visits where the person was logged in - which is the question you asked.
• Event-scoped, the denominator is events that carried logged_in - which excludes every hit that didn’t send it, and quietly inflates the rate.

Both numbers are computed correctly. Only one answers your question. Getting this wrong is how a report ends up confidently misleading, and it’s the sort of thing that’s very hard to notice later.

Rules of thumb: if the value could change between two pageviews in the same visit, it’s event scope. If it describes the person, it’s session scope.

Properties are allow-listed per site - enable the ones you want under Site settings → Properties, or allow all of them. Events that didn’t carry the property land in a labeled (none) bucket rather than vanishing from the total.

And keep personal data out of them. The DPA prohibits it, not just the docs.