What is a Sub ID? Affiliate Tracking Parameters Explained

A Sub ID is a custom tracking parameter appended to an affiliate tracking link that allows publishers to identify and segment their traffic sources, campaigns, ad creatives, and other variables. Sub IDs break down aggregate performance data into granular segments, telling you exactly which article, ad, email, or traffic source produced each conversion. They are essential for optimizing campaigns, scaling winners, and cutting losers.

Why Sub IDs Matter

Without Sub IDs, you know your overall stats — you sent 5,000 clicks and earned $400. But you don't know which of your 10 blog posts produced those conversions, whether your Facebook traffic outperformed your email list, or which ad creative drove the most revenue. You're flying blind.

With Sub IDs, you can answer questions like:

• Which blog post has the highest EPC?
• Which traffic source converts best for this offer?
• Which ad creative produces the lowest scrub rate?
• Which geo/device segment is most profitable?
• Which landing page variant drives the most conversions?

Every serious affiliate marketer uses Sub IDs. They transform raw data into actionable intelligence.

How Sub IDs Work

Sub IDs are added as URL parameters to your affiliate tracking link. Most CPA networks support multiple Sub ID slots (sub1, sub2, sub3, etc.), letting you track several variables simultaneously.

Example Tracking Link Structure

A standard affiliate link: https://track.network.com/click?oid=123&aid=456

The same link with Sub IDs: https://track.network.com/click?oid=123&aid=456&sub1=finance-blog&sub2=sidebar-banner&sub3=us-desktop

When a conversion happens, the network records those Sub ID values alongside the conversion data. You can then filter and group your reports by any Sub ID to analyze performance at a granular level.

Common Sub ID Naming Strategies

Sub ID Slot	Common Use	Example Values
sub1	Traffic source	seo, facebook, email, push, offerwall
sub2	Campaign or page	budget-app-review, insurance-comparison, homepage
sub3	Ad creative or placement	banner-top, text-link, sidebar, button-cta
sub4	Geography or device	us-mobile, uk-desktop, ca-ios
sub5	Additional segmentation	test-a, test-b, returning-user, new-user

There's no universal standard for how to organize Sub IDs — the best system is one that's consistent and meaningful to your workflow. Pick a convention and stick with it across all your campaigns. The concept is similar to how Google Analytics UTM parameters work for campaign tracking, but Sub IDs are specific to the affiliate network's tracking system.

Sub IDs in Practice: Step-by-Step

1. Plan your tracking structure — Decide what variables you want to track. At minimum, track traffic source and page/campaign. More experienced publishers track placement, device, and creative as well.
2. Add Sub IDs to your links — When generating tracking links in your CPA network dashboard, populate the Sub ID fields. On RevBoost, you can add up to 5 Sub IDs per link.
3. Deploy the links — Place the tagged links on your site, in your ads, in your emails, etc. Each placement should have its own unique Sub ID combination.
4. Wait for data — Give each Sub ID combination at least 100-200 clicks before drawing conclusions. Small samples produce misleading results.
5. Analyze performance — Pull reports filtered by Sub ID. Compare EPC, conversion rate, and earnings across segments.
6. Optimize — Scale the segments that perform well. Fix or cut the segments that underperform.

Dynamic Sub IDs

Many publishers use dynamic Sub IDs that automatically populate based on the traffic source. Instead of manually creating different links for every scenario, you use tokens or macros that your traffic platform fills in automatically. The IAB's measurement guidelines emphasize the importance of granular tracking parameters for accurate performance attribution in digital advertising.

For example, if you run ads on a traffic network that supports macros:

https://track.network.com/click?oid=123&sub1={source}&sub2={campaign_id}&sub3={creative_id}&sub4={country}

The traffic network replaces each token with the actual value for each click. This is especially valuable for media buyers running campaigns with hundreds of creatives across multiple geos.

Sub IDs for Offerwall Operators

If you run an offerwall or rewards site, Sub IDs serve a critical function: passing the user's ID to the CPA network so that when a conversion postback fires, you know which user to credit.

Typical offerwall Sub ID setup:

• sub1 — The user's unique ID on your platform (essential for crediting)
• sub2 — The user's device type or platform (web, ios, android)
• sub3 — The page or section where the offer was displayed

When the postback fires, the network sends back the Sub IDs, and your server uses sub1 to identify and credit the correct user.

Example: Sub ID Optimization

Scenario: You promote an insurance CPL offer across three blog posts, each tagged with a unique sub2 value.

sub2 (Page)	Clicks	Conversions	Conv. Rate	Earnings	EPC
cheap-car-insurance	800	48	6.0%	$864	$1.08
insurance-comparison	500	25	5.0%	$450	$0.90
save-money-tips	1,200	18	1.5%	$324	$0.27

Decision: The "cheap-car-insurance" page has the highest EPC ($1.08) and the best conversion rate. Double down on SEO for that page. The "save-money-tips" page has high traffic but very low conversion because the audience isn't specifically looking for insurance. Consider removing the offer from that page or replacing it with a more relevant one.

This level of insight is only possible with Sub IDs. Without them, you'd only see the blended $1,638 in earnings and have no idea which page is carrying the weight.

Related Terms

• EPC (Earnings Per Click) — Metric that Sub IDs help analyze at a granular level
• Pixel vs Postback Tracking — Postbacks return Sub ID values for server-side analysis
• CPA (Cost Per Action) — The pricing model where Sub IDs provide the deepest optimization value
• Offerwall — Uses Sub IDs to pass user IDs for automated crediting
• Scrub Rate — Can be tracked per Sub ID to identify traffic quality issues