When you apply block lists, our system checks that they are within our limits (i.e. they don't have too many entries).

If you try to apply a block list (or block lists) and you exceed our block list limits, you'll see a warning.

This won't prevent you from running the ad, but it will prevent you from running the ad on one or more of our five placements (on Facebook, in-stream videos and Instant Articles, and on Audience Network, in-stream videos, native, banner and interstitial ads and rewarded video).

Why?

Our auction system works best with plenty of options. If there are too many URLs on your block list, our delivery system doesn't have enough options to choose from.

Can I fix this?

If you see this error message and you're using a campaign-level block list, you might be able to block these URLs at the account or business level instead. At the campaign level, we set a lower limit of URLs that you can block than at the account and business level. Learn more

If not, you could remove one or more of your block lists, or some of the URLs on them; but don't do so if they're important. In making your decision, it might help you to see our current list of some of the apps, websites and Facebook Pages where your ads could appear (learn how to download it). This is because some URLs on your list might not be included in our network of placements, so removing them won't help.

* Nguồn: Facebook