What is a SubID?

What a SubID looks like

A SubID is just an extra query parameter on your affiliate link:

https://network.com/aff/offer?aff_id=123&subid=blog_vpn-review

Every network names the parameter differently:

• ShareASale — afftrack
• Impact — subId1 through subId4
• CJ — sid
• ClickBank — tid
• Rakuten — u1
• Most CPA networks — subid, aff_sub, or numbered s1-s5

Stick to letters, numbers, dashes, and underscores, and URL-encode anything else.

What to put in a SubID

Whatever dimension you want to optimize against:

• Placement — which page or post the link sits on: blog_vpn-review
• Traffic source / campaign — yt_video-42, fb_adset-7
• Creative or angle — creative-b, angle_speed
• Click ID — for paid traffic, pass your tracker's click ID into a SubID so conversions reconcile back to the exact click that drove them

Multi-level SubIDs (s1-s5)

Most CPA networks give you several slots so you can track multiple dimensions at once and pivot reports later:

?s1=facebook&s2=campaign-7&s3=adset-3&s4=creative-b&s5={click_id}

The network returns all five in the conversion postback, so you can break performance down by source, campaign, placement, creative, and click without running five separate links.

Reading SubIDs in your reports

The value comes back two ways: in the network's dashboard sub-report, and in your postback URL via a macro (e.g. &subid={subid} or &s1={s1}) so your own tracker records it. Pulling SubIDs through your postback is what lets you optimize at the placement and creative level instead of only the offer level.

Common SubID mistakes

• Spaces and special characters that break the URL — use dashes or encode them.
• Exceeding the length limit (often 50-255 characters) — values get truncated silently.
• Forgetting the postback macro — if you don't add it, the value never reaches your tracker.
• Putting PII in a SubID — never include emails or names; it's a privacy and terms-of-service problem.