Also known as: SubID, Sub-Identifier, S1-S5
A Sub-ID is a custom parameter appended to a tracking link that labels the exact source, placement or creative behind each click. Passed through to the broker and back on the postback, it lets a partner slice performance far below the campaign level.
When a partner builds a tracking link, they append one or more sub-ID parameters (often labelled S1 through S5, or sub1, sub2) populated by macros from the traffic source. Each click carries its own values, so a click from a specific push placement arrives at the broker tagged with that placement's identity. The broker's platform stores the sub-ID against the click.
When the referred client later converts, the broker fires a postback that returns the original sub-ID values to the partner's tracker. This closes the loop: the partner can now attribute the FTD not just to the campaign but to the precise placement and creative that produced it. That granularity is what lets a media buyer see that placement A converts at half the cost of placement B and reallocate budget accordingly, optimising far below the campaign level.
Decide what each sub-ID slot means, for example sub1 = source, sub2 = placement, sub3 = creative.
Insert the traffic source's macros so each click auto-populates the sub-ID values.
Test that the broker receives and stores the sub-ID values on the click.
Check that conversions post back the same sub-ID values to your tracker.
Group performance by sub-ID to see which placements and creatives actually convert.
Cut the losing sub-IDs and scale spend into the profitable ones.
Why it matters for partnership: Sub-IDs turn a single tracking link into a granular optimisation tool. They are how a media buyer knows that placement A converts and placement B burns cash, enabling them to cut losers and scale winners with precision.
An affiliate tags each traffic source with a sub-ID (sub1=push, sub2=native). When conversions post back, they see push traffic converts at half the cost of native and shift budget accordingly.
| Aspect | Sub-ID | UTM |
|---|---|---|
| Read by | Broker / affiliate platform | Your own analytics only |
| Returned on postback | Yes | No |
| Purpose | Conversion-level attribution | Session and traffic analytics |
Set a consistent sub-ID naming convention across every campaign so your reports stay comparable and you never lose track of what each label means.
Using cryptic or inconsistent sub-ID values that you cannot decode weeks later, making the data useless for optimisation.
UTMs are read by your own analytics; sub-IDs are passed to and returned by the broker/affiliate platform for conversion-level attribution.