Bid Selection

After all eligible creatives are collected for an impression, the system selects the winning bid.

Selection algorithm

1. Filter eligible creatives: Only creatives that pass the delivery ratio check (ratio > random) or have a CPC segment match are kept

2. Random shuffle: All eligible creatives are randomly shuffled (for fairness when prices are equal)

3. Sort by price: Creatives are sorted by effective CPM in descending order, with currency conversion applied

4. Select winner: The highest-priced creative wins the impression

Price priority

The effective CPM for a creative is determined by the first available value:

1. Segment CPM (from CPC segment match) -- highest priority

2. Split CPM (from the split's cpm field, if > 0)

3. Line item rate (from delivery.rate) -- base price

Currency conversion

All prices are converted to the bid request's target currency (from bidRequest.cur, default USD) before comparison. The conversion uses rates from the Prebid currency CDN, updated every hour.

If conversion fails for a creative (unknown currency), that creative is deprioritized in the sort.

Bid response

The winning creative is returned as an OpenRTB 2.5 bid response:

{
  "id": "response-uuid",
  "cur": "USD",
  "seatbid": [
    {
      "seat": "Advertiser Name",
      "bid": [
        {
          "id": "bid-uuid",
          "impid": "impression-id",
          "price": 3.50,
          "crid": "creative-id",
          "adm": "<ad markup>",
          "adomain": ["advertiser.com"],
          "w": 300,
          "h": 250,
          "dealid": "deal-external-id",
          "ext": {
            "lineItemId": 12345,
            "splitId": 1,
            "splitName": "Split A",
            "segmentId": 10
          }
        }
      ]
    }
  ]
}

Bid ext fields

Field	Presence	Description
lineItemId	Always	The line item that won
splitId	When from a split	The split identifier
splitName	When from a split	The split name
segmentId	When CPC	The matched CPC segment identifier

No bid

If no creative passes all checks for any impression, the DSP returns HTTP 204 (No Content).