Sub IDs are labels you add to tracking links. They turn a single total into a breakdown of exactly where conversions came from.
Main points
- Sub IDs are extra values in a tracking link that label where a click came from.
- Use them for the source, placement, campaign and creative you want to compare.
- Network reports group clicks and conversions by sub ID.
- Keep personal data out of sub IDs.
Without sub IDs, a report tells you that an offer converted 20 times. With them, it tells you that 15 came from one page and five from a newsletter, and that the sidebar banner produced none.
How sub IDs work
A tracking link has fields for your own labels, often named sub1, sub2 and so on. Whatever you put there is recorded with each click and conversion.
Example labels:
| Field | Example value | Tells you |
|---|---|---|
| sub1 | newsletter | Traffic source |
| sub2 | oct-issue | Campaign |
| sub3 | top-banner | Placement |
| sub4 | headline-b | Creative or test version |
Reading the report
Most networks let you group results by each sub ID. Compare:
- clicks and conversions per label
- conversion rate
- lead approval rate, for lead offers
- earnings per click
Pro tip
Agree a simple naming scheme and stick to it: lowercase, no spaces, consistent order. Messy labels make reports hard to compare later.
Acting on the data
- Find placements with clicks but few conversions.
- Check whether the issue is the traffic, the page or the offer.
- Pause what doesn’t work and give more space to what does.
- Test one change at a time and label it with its own sub ID.
Compliance alert
Never put names, email addresses, phone numbers or other personal data in sub IDs. They’re stored in tracking systems and shared with networks and advertisers.
Combining sub IDs with other tracking
Sub IDs work best alongside postback tracking, which reports conversions reliably, and an understanding of attribution windows, which explains why conversions sometimes appear days after the click.
Frequently asked
How many sub IDs can I use?
It depends on the network. Many offer several fields, such as sub1 to sub5, so you can label different details separately.
Are sub IDs the same as UTM parameters?
They do a similar job. UTM parameters are read by analytics tools on your own site, while sub IDs are read by the affiliate network.
How much data do I need before deciding?
Enough clicks for differences to be meaningful. Small samples can be misleading, so be patient before cutting a source.
This article is general information for marketers, not legal advice. Advertising, privacy and consumer protection rules vary by country and change over time, so check the current rules and your network’s terms, and get legal advice where needed before running campaigns.