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SubID, short for sub-identifier, is an additional parameter passed with an affiliate link to provide more detail about a click and its subsequent conversion. Affiliates and media buyers can use SubIDs to identify specific traffic segments, such as creatives, placements, GEOs, devices or audience groups.

SubIDs are often used together with a tracker for affiliate traffic analytics and campaign management. However, a SubID is not a universal click identifier, and it does not automatically pass through every stage of the conversion funnel. Whether the parameter is preserved depends on the traffic source, tracker, affiliate program and the way the integration is configured.

In simple terms, a SubID adds context to a click. This makes it possible to move beyond campaign-level statistics and determine which creative, placement or other traffic segment generated a registration, FTD or another target action.

Why Do Affiliates Use SubIDs?

The main purpose of a SubID is to make campaign data more granular. The same offer can perform very differently depending on the traffic source, creative, GEO, device or other characteristics of the traffic.

SubIDs can be used to:

  • Break down campaign data by segment. Affiliates can label individual creatives, placements, GEOs, devices or audience segments and analyze them separately.
  • Identify effective combinations. More granular tracking makes it easier to see which campaign elements generate conversions and which require optimization.
  • Optimize ad spend. If a particular segment consistently underperforms, it can be adjusted or paused without stopping the entire campaign.
  • Compare traffic quality. SubID-level reporting can be used to compare not only conversion volume but also downstream metrics such as FTDs, retention and other available quality indicators.
  • Analyze segment-level economics. When cost and revenue data are available, SubIDs can help break down CAC, ROI and other financial metrics by traffic segment. The SubID itself does not calculate these metrics - it provides the link between the metrics and the relevant segment.

For example, if a campaign contains ten creatives, campaign-level reporting may show the combined result of all ten. With separate SubIDs, a media buyer can analyze the performance of each creative individually.

How Does a SubID Work Technically?

A SubID is passed as an additional parameter in a URL. For example:

https://offer-link.com/?sub1=facebook&sub2=creative_01&sub3=us

In this example:

  • sub1 identifies the traffic source;
  • sub2 identifies the creative;
  • sub3 identifies the GEO.

The parameter can then be preserved and passed between tracking systems and the affiliate program. A typical setup may look like this:

  1. A user clicks an ad containing SubID parameters.
  2. The tracker records the click and stores the parameters together with other click data.
  3. When the user reaches the offer, the required parameters need to be passed correctly and retained by the affiliate platform or advertiser.
  4. After a registration, FTD or another conversion event, the affiliate program sends conversion data through the configured tracking mechanism, such as a server-to-server postback for transmitting conversion data.
  5. The tracker matches the conversion to the original click and its parameters, allowing the result to be analyzed by the relevant traffic segment.

This does not mean that a SubID is automatically returned in every postback. Correct attribution requires the traffic source, tracker and affiliate program to support the relevant parameter mapping and be configured correctly.

For this reason, it is good practice to run a test click before launching a campaign and verify that the required values are preserved throughout the tracking flow.

SubID vs. Click ID: What Is the Difference?

SubID and click ID are both used in tracking, but they serve different purposes.

A click ID is an identifier for a specific click. It is typically generated automatically by a tracking system or advertising platform and is used to associate an individual click with a subsequent conversion.

A SubID is an additional parameter used to label a click or traffic segment. Its value and structure are defined by the campaign's tracking setup.

For example, a click ID may identify one specific user click, while a SubID can indicate that the click came from a particular creative, placement or GEO.

SubIDs therefore do not replace click IDs. In many tracking setups, both can be used at the same time.

Common SubID Structures and Their Uses

Different advertising platforms, affiliate programs and trackers may use different parameter names and support different numbers of SubID fields. A structure such as sub1, sub2, sub3 is common, but it is not a universal standard.

For example, an affiliate can assign:

  • sub1 - traffic source or advertising platform;
  • sub2 - creative ID;
  • sub3 - GEO or language;
  • sub4 - device or placement;
  • sub5 - audience segment or traffic format.

Using a consistent structure makes reporting easier, especially when the same setup is applied across multiple campaigns.

At the same time, sub1, sub2 and sub3 should not be treated as universal definitions. Their names, available slots and functions depend on the specific platform and integration.

SubIDs and API-Based Data Exchange

APIs can be used to automate data exchange between advertising platforms, trackers, affiliate programs and internal reporting systems.

For example, an API can automatically retrieve spend and campaign data from an advertising platform and combine it with conversion data. If the relevant systems support SubID-based reporting, these parameters can be used as an additional dimension in automated reports.

An API does not replace URL parameters or the conversion-tracking mechanism itself. The exact capabilities depend on the API provided by the relevant platform and the available integrations. For more information, see the 3S.INFO guide to API-based data exchange between platforms.

How to Structure SubIDs Properly

A consistent naming system makes SubID data much easier to analyze.

Use a clear structure. For example, assign each slot to a specific type of information: traffic source, creative, GEO, device or placement.

Avoid combining too many attributes unnecessarily. A value such as facebook_creative01_us can work, but separate parameters such as sub1=facebook, sub2=creative01 and sub3=us provide a cleaner structure for filtering and reporting when the platform supports multiple fields.

Check technical restrictions. A tracker, advertising network or affiliate program may impose limits on parameter length, allowed characters or URL formatting. These requirements should be checked before launching a campaign.

Keep naming consistent. If sub2 represents the creative in one campaign but the GEO in another, comparing data becomes much harder. Consistency is especially important when running multiple campaigns or working with large volumes of traffic.

Test the full parameter flow. The fact that a SubID appears in the original URL does not mean that it will reach the final reporting system. Run a test click and verify that the value is retained by the tracker and associated correctly with the conversion data.

Common SubID Mistakes

  • Relying only on campaign-level statistics. Without additional segmentation, differences between creatives, placements and other traffic segments can disappear in the overall campaign figures.
  • Putting too much information into one parameter. Complex values make filtering and reporting harder and increase the risk of mistakes. When multiple parameters are available, it is usually more practical to distribute different attributes between them.
  • Failing to test SubID passing. A parameter may be present in the original URL but disappear somewhere between the traffic source, tracker and affiliate platform. Testing should therefore cover the full path from click to conversion tracking.
  • Confusing SubIDs with click IDs. Click IDs and SubIDs can work together, but they are not interchangeable. A click ID typically identifies a specific click, while a SubID provides additional context for segmentation and reporting.
  • Treating a SubID as a quality metric. A SubID only labels or groups data. To assess traffic quality, affiliates still need to analyze actual performance metrics such as conversions, spend, revenue, FTDs, retention and other available indicators.
  • Ignoring SubID data when scaling. Before increasing campaign spend, it is useful to understand which traffic segments are responsible for the results. Otherwise, scaling can hide significant differences between stronger and weaker parts of the campaign.

SubIDs are a simple technical tool that become increasingly useful as the number of campaign tests and traffic segments grows. A well-structured parameter system helps affiliates connect clicks and conversions with specific campaign elements instead of relying only on aggregated statistics.

For tracking infrastructure, explore trackers and TDS for media buying and iGaming. Current tracker and TDS offers are also available in the 3S.INFO tracker and TDS promo code section. Affiliates can find offers to test after registering with the 3SNET CPA network.