What is a Sub ID?

A sub ID (subid, sub1–subN) is an extra parameter in tracking links and postbacks that lets a media buyer break down stats inside one campaign: creative number, ad set, placement, GEO split, landing, A/B stream. The tracker stores sub values on the click row and exposes them in reports.

Example URL: https://track.domain/click?campaign=1&sub1={ad_id}&sub2={placement}&sub3={creative}. Macros are filled by the ad platform or manually. On conversion the network may echo subs in the postback for reconciliation.

Why sub IDs matter

• Optimization — cut losing creatives without separate tracker campaigns.
• Scaling — see EPC by placement and raise bids on winners.
• AM communication — pass subs when disputing lead quality.

Conventions and limits

Sub field count depends on tracker and network (often 5–20). Names sub1…sub5 are a CPA de facto standard. Do not confuse sub ID with click ID: click ID is unique per click and required for attribution; subs are your custom labels. Long values and special chars need URL encoding.

Mistakes

Swapped sub schema between campaigns, empty macros on non-dynamic buys, subs overwritten by a smart link without documented rules.

See also: click ID, tracker, postback, UTM parameters.