We're close to launching GrowthBook and have one final question! Our product has both logged-in and anonymous users. Your FAQ <https://docs.growthbook.io/faq#what-do-i-use-for-an-id-attribute-in-the-sdk-if-my-users-arent-logged-in |suggests> we use two identifier attributes, but as far as we can tell, we <https://i.imgur.com/vQOJHGN.png |can only select one>. How might we achieve that suggestion from your FAQ? The goal is for any logged-in user to always see the same A/B test, but that A/B test might also be applicable to anonymous users.

The

user_id_or_anonymous_id

will cause users to potentially switch variations when they log in. Our recommended approach is to pick just one identifier type for each experiment. Depending on the specific experiment, you might pick

user_id

or

anonymous_id

. As a general rule of thumb, if the test is shown primarily to only logged-in users, then pick

user_id

. Otherwise, pick

anonymous_id

. If a test has a large amount of both logged-in and anonymous users, I would usually just use

anonymous_id

to split traffic. Users who switch devices or clear cookies may see multiple variations, but for most tests and products, that should be a relatively small percent of users and unless it's something super critical like pricing, not a huge deal if a few people see both variations.

Thank you!