(root)

BidRequest

The top-level container for an auction. Carries the impressions on offer plus everything the bidder needs to value them.

Fields

Field	Type	Level	Description
id	string	required	ID of the bid request, assigned by the exchange.
imp	object[]	required	The impressions on offer. At least one is required.
site	object	recommended	Details of the publisher website. Mutually exclusive with app.
app	object	recommended	Details of the publisher application. Mutually exclusive with site.
device	object	recommended	The end user's device.
user	object	recommended	The human user of the device.
tmax	integer	optional	Maximum time in milliseconds the exchange will wait for a response.
at	integer	optional	Auction type. Defaults to 2, second price.
cur	string[]	optional	Allowed bid currencies, ISO-4217.
test	integer	optional	Test mode. Defaults to 0.

Example

{
  "id": "80ce30c53c16e6ede735f123ef6e32361bfc7b22",
  "at": 2,
  "tmax": 120,
  "cur": ["USD"],
  "imp": [
    {
      "id": "1",
      "bidfloor": 1.50,
      "banner": { "format": [{ "w": 300, "h": 250 }] }
    }
  ],
  "site": {
    "id": "102855",
    "domain": "example.com",
    "page": "https://example.com/article"
  },
  "device": { "devicetype": 2, "os": "macOS" },
  "user": { "id": "55816b39711f9b5acf3b90e313ed29e51665623f" }
}

What matters in practice

Two things here account for a large share of confused debugging. First, a request carries exactly one of site, app or dooh — never two — so a bidder reading site on in-app traffic will find nothing. Second, tmax is the whole reason otherwise valid bids never appear in reporting: respond after it and the bid is simply discarded, with no error and no record on the buy side. When win rate looks inexplicably low, compare your response latency against tmax before looking at price.

Related objects

Field names, types and requirement levels from the IAB Tech Lab OpenRTB 2.6 specification (2.6-202211), verified 30 July 2026. The practice notes are not spec text.