What is the x-openrtb-version HTTP header?
Answer
It is the custom HTTP header OpenRTB defines for version signaling on the wire: the sender of a bid request declares the protocol version it speaks, for example x-openrtb-version: 2.6. The body should also be sent with Content-Type: application/json. The header names the version line, not the dated snapshot, so 2.6 traffic from 2022 and 2025 both say 2.6 even though the field sets differ; that finer distinction is exactly why validating against a specific snapshot matters.
Go deeper
More questions on debugging, no-bids, and validation
- Why is my bidder not receiving bid requests? Work the path from the exchange inward: confirm the endpoint the exchange has on file matches what you deployed (scheme, host, path), that your endpoint returns a well-formed response or HTTP 204 quickly enough to stay under the exchange's timeout, and that traffic filters on the exchange side (geo, media type, QPS caps, pretargeting) are not excluding you.
- Why is my bid rate low even though I receive requests? Start by separating deliberate no-bids from failures.
- How do I find out why my bids are losing auctions? Ask for loss reasons via the loss notice URL.
- How do I debug a systematic OpenRTB no-bid? If the bidder returns a BidResponse with nbr set, the code tells you where to look: nbr 2 is Invalid Request, which means the bidder could not parse or accept your bid request, so run the request through a validator before anything else.
- What does HTTP 204 mean in OpenRTB, and how is it different from nbr? HTTP 204 No Content is the spec's preferred way for a bidder to say it has no bid: no body, cheapest possible round trip.
- How do I validate an OpenRTB bid request? Paste it into a validator that checks against the actual spec catalog, not just JSON syntax.
All 93 questions are listed in the OpenRTB FAQ.