Tracking & optimisation · also called subid, sub-ID, tracking ID, sub parameter
Sub ID
A sub ID is a custom label a publisher passes to a feed or network with each visit, so reported revenue can be broken down by that label.
A feed reports earnings in totals unless told how to slice them. A sub ID is the slicing instruction: a value the arbitrageur attaches to each visit, which the feed stores and returns next to the revenue. The name comes from affiliate networks, where partners labelled their sub-sources this way.
What goes in the sub ID is the operator's choice: a campaign name, an ad ID, a placement, or the tracker's Click ID. Many feed providers offer several sub ID fields. On Google's own products the nearest equivalent is the Channel ID, a reporting bucket that groups traffic. Google notes that channel-level statistics appear only once a channel has enough activity, which limits how fine the slicing can be.
Sub IDs do two jobs. They let the tracker match revenue to cost. And they isolate risk: with each traffic source in its own bucket, a quality problem or a clawback can be traced to its origin and removed without guessing. Feeds may demand this separation as a condition of approval.
An example
Say total revenue is $270 on 1,000 visits. By sub ID: "taboola_siteA" earned $210 from 600 visits ($0.35 each) and "taboola_siteB" earned $60 from 400 ($0.15 each). At a $0.20 cost per visit, A is profitable and B is not.
Related terms
Channel ID (custom channel)
A channel ID is a label attached to search ad requests so that revenue and clicks can be reported separately for each page, campaign or traffic source.
Click ID
A click ID is a unique code an ad platform or tracker attaches to each ad click so that later events can be matched back to that exact click.
Tracker (campaign tracking platform)
A tracker is software that records every click an arbitrageur buys, matches it to the revenue it later earns, and reports profit by campaign, ad and keyword.
Postback (server-to-server tracking)
A postback is a message sent directly from one company's server to another's to report that a tracked click produced a conversion or revenue.
Keyword-level reporting
Keyword-level reporting breaks down clicks and revenue by the individual keyword or related search term the visitor clicked on the landing page.
Placement
A placement is the specific website, app, section or screen position where an ad appears.
Sources: Google AdSense Help: Custom channel