A floor is the lowest price you will accept. Set it too high and you reject real demand; too low and you give inventory away. Prebid’s Floors module turns that one number into a rules table that can vary by size, device, and audience.
A price floor is the minimum bid you will accept for an impression. Anything below it is rejected before it can win.
| Floor type | Where the value comes from |
|---|---|
| Hard-coded | Static values you set in config. |
| Dynamic | Fetched or computed in real time from a floor provider, based on observed demand. |
The rules schema
The Floors module matches each bid against a schema dimensioned by ad unit, media type, size, device, and first-party data, so a 300x250 on mobile can floor differently than a 728x90 on desktop. floorMin sets an absolute minimum, and enforcement decides whether sub-floor bids are dropped or merely flagged.
Quick check
An enforced floor is $0.50 and a bidder returns $0.30. What happens to that bid?
Watch out
A mis-keyed floor rule (a wrong size or dimension) can accidentally match everything and reject every bid. "Suddenly zero bids" after a floors change is almost always this.