UTM Tags vs Sub IDs: Passing Data Through Your Funnel

Two systems with different jobs

Most funnels carry two kinds of labels on the same URL. UTM tags (utm_source, utm_campaign and friends) tell a web analytics tool where a visit came from. Sub IDs (sub1 to sub15, aff_sub, s2, depending on the platform) carry values to the tracker and on to the affiliate network, so a conversion can be tied back to the exact ad, placement or creative.

The confusion starts when one is used for the other's job. UTM tags are read in the browser and often stripped by redirects, privacy tools or the offer page itself. Sub IDs travel server side with the click and come back in the postback. If the number you need for a buying decision only exists in a UTM tag, it will not be in your conversion data.

What UTM tags are for

Use UTM tags when the landing page is your own and you run web analytics on it. They answer questions like "which source brings visitors who scroll to the form" or "which newsletter drives returning visits". They are a reporting convention, not a tracking mechanism: nothing guarantees they survive to the conversion.

• Keep them lowercase and consistent: facebook and Facebook become two sources.
• Do not put personal data in them. They end up in logs, referrers and screenshots.
• If the offer is on an affiliate network's domain, assume the UTM tags stop at the offer page.

What sub IDs are for

Sub IDs are slots on the tracking link that the tracker stores with the click. Typical values are the ad platform's campaign, ad set and ad IDs, the placement or site ID, the creative name and the keyword. Because they are stored with the click, every conversion that comes back by postback inherits them, and you can group revenue and ROI by any of them.

There is a second set of sub IDs: the ones you pass on to the affiliate network. The network usually gives you a few free slots, and one of them must carry the tracker's click ID. The rest can repeat values you want to see in the network's own statistics, such as the source or the creative.

Mapping ad macros to sub IDs

Ad platforms fill their own macros at click time. Your job is to put each macro into a sub ID slot once, in the traffic source template, and never think about it again. A typical layout:

In XPNSR Tracker, traffic source presets fill this mapping for the common platforms, and the report builder groups by any sub ID. Whatever tool you use, keep the same slot for the same meaning across all sources, so a report on sub4 always means placements.

Naming rules that survive scale

• IDs over names. Names change when someone renames an ad; IDs do not. Store the ID and look up the name when you need it.
• One meaning per slot. Never reuse sub3 for creatives on one source and keywords on another.
• No spaces or special characters in values you type by hand. Use letters, digits, dashes and underscores.
• Document the layout in one shared place, so a new buyer does not invent a second one.

A five-minute check

1. Open your ad's final URL with the macros filled in (most platforms have a preview).
2. Click through and find the click in the tracker's click log. Every sub ID should show a real value, not the macro name in braces.
3. Open the offer URL the tracker produced and confirm the click ID is in the slot the network expects.
4. Fire a test conversion and check it arrives on that click with all sub IDs intact.

If a value shows up as {adset_id} literally, the macro name is wrong for that platform. If it is empty, the platform does not fill that macro for this ad type. Both are fixed in the source template, not in each campaign.