Imp.exp

Advisory number of seconds that may pass between the auction and the moment the impression is actually shown. Added in OpenRTB 2.4.

CurrentintegerOptionalSince 2.4

Field facts

Path: imp.exp
Object: Imp
Type: integer
Requirement: Optional
Added: OpenRTB 2.4
Spec section: 3.2.4

How it is used

It matters when ads are fetched before they are displayed: cached interstitials, prefetched video, CTV breaks, and DOOH loops. Buyers use it to judge whether their price and creative will still hold when the ad finally shows. Bid.exp is the buyer's side of the same question: how long it is willing to wait.

Example

Where the field sits in a payload, with everything else left out:

{
  "id": "req-1",
  "imp": [
    {
      "exp": 300
    }
  ]
}

Common mistakes

Sending milliseconds instead of seconds turns a 300 second window into more than three days.

Version history

Added in OpenRTB 2.4, and present in the latest snapshot. The table shows how each version's spec text types the field.

Versions	Type in the spec	Required	Deprecated
2.4	integer	No	No
2.5 to 2.6-202606	integer	No	No

Related fields

Other Imp fields

For a walkthrough of the whole object, read Bid request anatomy.