${AUCTION_AD_ID}

What it expands to

ID of the ad markup the bidder wishes to serve, from bid.adid.

Expands in notice URLs and adm with bid.adid, the id of the ad markup the bidder chose.

What to watch for

If your creatives rotate under one bid id, adid is what distinguishes them in delivery logs. Leave bid.adid unset and the macro expands empty.

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_AD_ID: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_PRICE}