The early period after launching or significantly editing an ad set when the algorithm is still figuring out who to show your ads to. Performance is volatile here and you can't trust the numbers yet. The system needs around 50 conversion events per week to exit learning.
What triggers a new learning phase:
- Creating a new ad set
- Pausing for 7+ days then reactivating
- Changing targeting significantly
- Adjusting budget by more than 20% at once
- Adding or removing ads
- Changing the optimization event