How soon remarketing lists can start working
Find out the minimum size for a remarketing list, learn how quickly visitors can get added to a list, and understand which ad gets shown when a customer is on more than one of your remarketing lists.
Number of visitors needed for a remarketing list
A remarketing list must have at least 100 active visitors within the last 30 days before you can show an ad to people on the list when they visit a Display Network site. A remarketing list for Google search ads needs to have a minimum number of 1000 cookies before the list can be used to tailor your search ads. This helps protect the privacy of those who make up your list.
There's no maximum limit to the number of visitors you can add to your list. Your list will grow based on the number of people who visit the pages in your site that include your remarketing tag.
How quickly visitors are added
Visitors are added to a remarketing list within seconds after visiting a page with a remarketing tag. Every time someone visits a page containing this tag, his timestamp is updated so he remains on the list for the amount of time specified in the membership duration of the list. For example, if you've set your remarketing list's membership duration at 30 days, then your list must have at least 100 visitors from the last 30 days to be eligible for targeting on the Display Network.
What happens when people are on more than one list
If people visit multiple pages on your site containing remarketing tags, they can be added to more than one of your remarketing lists. When this happens, all the ads included in the remarketing campaigns for those lists are eligible to serve. The ad with the highest ad rank will then compete for placement in the auction.