Bid.exp

How many seconds the bidder is willing to wait between the auction and the actual impression. Advisory; added in 2.4.

CurrentintegerOptionalSince 2.4

Field facts

Path: seatbid.bid.exp
Object: Bid
Type: integer
Requirement: Optional
Added: OpenRTB 2.4
Spec section: 4.2.3

How it is used

Cached inventory, such as app interstitials or server-stitched video, can render minutes after the auction, and the exchange may drop bids whose expiration it expects to miss. The spec's guidance suggests rough values from about one minute for web to 30 minutes or more for interstitials. Whether a late impression is still billable is a contract question that this field does not settle.

Example

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

{
  "seatbid": [
    {
      "bid": [
        {
          "exp": 300
        }
      ]
    }
  ]
}

Common mistakes

Confusing it with BidRequest.tmax. exp is in seconds and covers the delay after the auction, not the bidding window.

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 to 2.5	integer	No	No
2.6-202210 to 2.6-202606	integer	No	No

Related fields

Other Bid fields

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