${AUCTION_LOSS}

What it expands to

Loss reason code; the code list lives in OpenRTB 3.0.

Expands only in the loss notice URL (lurl) with the loss reason code, added in 2.5. The code list itself is maintained in the OpenRTB 3.0 / shared documentation.

What to watch for

Outside lurl it has no defined value. Every loss code has its own page here; start from the loss reason reference to decode what the exchange is telling you.

Encoding

When a macro rides inside another URL as a query parameter, the expanded value must survive URL parsing: exchanges support suffixed forms like ${AUCTION_LOSS:B64} (base64) where documented, and values containing reserved characters must be percent-encoded. An unencoded expansion is the most common reason a notice URL truncates at the first ampersand.

Related

• All substitution macros
• Where nurl, burl, and lurl fire in the delivery flow
• Loss reason codes
• ${AUCTION_ID}
• ${AUCTION_BID_ID}
• ${AUCTION_IMP_ID}
• ${AUCTION_SEAT_ID}
• ${AUCTION_AD_ID}