Tag links GA4 will file in the right channel.

What UTM parameters tell GA4

UTM parameters are tags you add to a link so that GA4 knows where a visit came from. Google says to always use utm_source, utm_medium and utm_campaign, and missing values show up as “(not set)” in reports. These three are also the only parameters that affect the default channel. Use the source for the referrer, such as a site, a newsletter or a publication; the medium for the type of traffic, such as email, cpc or referral; and the campaign for the promotion itself.

The others add detail. utm_term holds a paid keyword and utm_content tells apart creatives or links within one campaign. utm_id is the campaign ID GA4 uses to join imported cost data to your campaigns. utm_creative_format and utm_marketing_tactic are collected, but Google says they aren’t currently reported in GA4 properties, so don’t plan reports around them.

The rules that decide the channel

GA4’s default channel group sorts tagged visits by source, medium and campaign. Search, social, video and shopping channels also depend on Google’s published list of sources, and newer names such as threads and x.com aren’t on it. These rules decide where most links end up:

• Paid channels need a medium matching ^(.*cp.*|ppc|retargeting|paid.*)$: anything containing cp, such as cpc, plus ppc, retargeting and anything starting with paid.
• Paid Search, Paid Social and Paid Video also need a source on Google’s list of search, social and video sites. Without one, most paid traffic lands in Paid Other, including paid traffic from platforms missing from the list.
• The list includes google but not google.com, so google / cpc is Paid Search and google.com / cpc is Paid Other.
• Organic Social needs a listed social source or a medium such as social, social-media or sm, so organic posts on unlisted platforms still count if the medium is social.
• Email needs the source or the medium to be exactly email, e-mail, e_mail or e mail. A medium of newsletter doesn’t count.
• Referral needs a medium of referral, app or link.
• Visits from known AI assistants, such as ChatGPT or Gemini, go to the AI Assistant channel, which GA4 assigns itself from the referrer; a medium of ai-assistant puts a tagged link there too.
• Traffic that matches no rule is reported as Unassigned.

Mistakes that split or lose data

In audits we often see the same few problems:

• Mixed capitals. The channel rules ignore case, but reports don’t: Facebook and facebook are separate rows. Google recommends lowercase as standard practice.
• Inconsistent spelling. spring-sale, spring_sale and SpringSale are three campaigns in your reports. Agree one spelling and one separator, and keep the values you use in a shared list.
• Invented mediums. With a source GA4 doesn’t recognise, mediums such as newsletter, post, qr or print end up in Unassigned.
• Tagged internal links. GA4 doesn’t start a new session when it meets new campaign values, and the session keeps its original source. The new values are still attached to the events they arrive with and used for event-based attribution, so your own banner can take credit for key events another channel earned. GA4’s ecommerce events include view_promotion and select_promotion for measuring internal promotions such as banners.

Business Profiles, QR codes and print

Tag the website link on your Google Business Profile. Without UTM parameters, profile clicks blend into the rest of your organic search traffic; with them, you can report on the profile separately. Keeping google as the source and organic as the medium leaves those visits in Organic Search, and a campaign value such as gbp picks them out.

GA4 has no offline or QR channel, so links on posters, packaging or other printed material land in Unassigned unless they match another rule. Choose one medium for them, such as qr or print, use it every time, and create a custom channel group with a channel for that medium. Traffic goes to the first channel it matches in the group’s order, so place the new channel above any broader one that would also catch it. Custom channel groups can be applied to reports retroactively, so data you have already collected is included.