The Magnite banner response MIME type differs from the requested markup format.

What it means

The Magnite banner response MIME type differs from the requested markup format. This check applies to the selected vendor contract and integration direction.

Why it matters

The declared profile checks the published partner contract alongside canonical OpenRTB. It does not verify runtime approval or account configuration.

How to fix it

Use an option offered by the matching request. Check the request and response together at the reported path.

Example that trips it

Request:
{
  "id": "request-1",
  "imp": [
    {
      "id": "imp-1",
      "banner": {
        "w": 300,
        "h": 250,
        "ext": {
          "rp": {
            "mime": "text/html"
          }
        }
      }
    }
  ]
}

Response:
{
  "id": "request-1",
  "seatbid": [
    {
      "seat": "buyer-code",
      "bid": [
        {
          "id": "bid-1",
          "impid": "imp-1",
          "price": 1.5,
          "ext": {
            "rp": {
              "response_format": 1,
              "mime": "application/javascript"
            }
          }
        }
      ]
    }
  ]
}

Profile magnite, OpenRTB 2.6-202606. The fixture asserts openrtb.profile.magnite.mime_mismatch at seatbid[0].bid[0].ext.rp.mime.

Check your payload

Paste a bid request or response into the tester to see whether this code fires against it, or gate on the id in CI with the CLI: the id is stable, wording is not.

• Primary protocol documentation
• Replayable source fixture

Back to the full diagnostic code reference.