UTM Parameters Guide: Build, Name and Fix "Unassigned" in GA4

By the Mayab Media Team · Level: Beginner · Time: 40 minutes

You sent a newsletter, ran a few social posts and printed a QR code. In GA4, most of that traffic lands in Direct, Referral, or the worst bucket of all: Unassigned. You can't tell which campaign worked, so you can't do more of it.

UTM parameters fix this. They are small tags added to the end of a link, like ?utm_source=newsletter&utm_medium=email&utm_campaign=spring_sale. When someone clicks, GA4 reads them and records where the visit came from. But GA4 is strict. It sorts traffic into channels with fixed rules, and a medium it doesn't recognize ends up as Unassigned. Values are also case sensitive, so Email and email become two rows.

This guide shows you how to build UTM links, which values GA4 expects, how to set a naming system your whole team can follow, and how to find and fix Unassigned traffic.

Quick answer

1. Always set utm_source, utm_medium and utm_campaign. Use lowercase and no spaces.
2. Pick utm_medium values that GA4's default channel rules recognize: email, cpc, social, display, affiliate, referral, sms.
3. Build links with Google's Campaign URL Builder or a shared spreadsheet.
4. Never put UTMs on links within your own site. Keep Google Ads auto-tagging on instead of adding UTMs to Google Ads.
5. To fix Unassigned, check Session source / medium for unknown mediums, correct future links, and optionally create a custom channel group.

Before you start

• Access: Viewer access to GA4 to check reports. Editor access if you want to create a custom channel group.
• A list of your channels. Newsletter, social profiles, paid social, partners, print, SMS, and so on.
• A shared place for links. A spreadsheet works fine. The goal is one source of truth.
• Time: about 40 minutes to set up the naming rules and audit current traffic.

The parameters GA4 reads

Parameter	What it describes	Example
utm_source	Who sent the visit	newsletter, facebook, partner-blog
utm_medium	The channel type	email, cpc, social, referral
utm_campaign	The campaign or promotion	spring_sale_2026
utm_content	Which ad, link or creative	hero_button, video_a
utm_term	Paid keyword (mostly for search ads)	running+shoes
utm_id	Campaign ID, used for cost data imports	cmp_0412
utm_source_platform	The buying platform	meta_ads

GA4 also lists utm_creative_format and utm_marketing_tactic, but Google says they aren't currently shown in GA4 reports. You can skip them.

Step 1: Learn which mediums GA4 recognizes

This is the step most people skip, and it's the reason for most Unassigned traffic. GA4 decides the Default channel group from your source and medium using fixed rules. Here are the main ones for manually tagged links:

Channel	Rule (simplified)	Safe medium to use
Email	source or medium is email, e-mail, e_mail or e mail	email
Organic Social	source is a known social site, or medium is social, social-network, social-media, sm	social
Paid Social	source is a known social site and medium matches paid patterns (cpc, ppc, paid…, retargeting)	paid_social or cpc
Paid Search	source is a known search engine and medium matches paid patterns	cpc
Display	medium is display, banner, expandable, interstitial or cpm	display
Affiliates	medium is affiliate	affiliate
Referral	medium is referral, app or link	referral
SMS	source or medium is sms	sms
Paid Other	medium matches paid patterns, but the source isn't a known social or search site	cpc
Unassigned	nothing matched	avoid

Channel rules aren't case sensitive, but your reports are. So Email still lands in the Email channel, but appears as a separate row from email under Session medium. Lowercase avoids that mess.

Notice what's missing. Mediums like newsletter, qr, print, post, story, bio or whatsapp match no rule. If the source also doesn't match a known site, the visit becomes Unassigned.

Step 2: Set a naming convention

Write your rules down once. Share them. Here's a simple template that fits the channel rules.

Use case	utm_source	utm_medium	utm_campaign
Monthly newsletter	newsletter	email	2026-11_newsletter
Organic Instagram post	instagram	social	fall_launch
Paid Facebook ad	facebook	paid_social	fall_launch
LinkedIn profile link	linkedin	social	profile
Partner blog mention	partner-blog	referral	guest_post
QR code on a flyer	flyer	offline	fall_event
Text message	sms	sms	fall_reminder

The QR code example is a special case. There's no default channel for print. You can use referral, or keep offline and map it with a custom channel group (Step 5).

Rules that save you later:

• Lowercase only. Google recommends it, and it avoids split rows.
• No spaces. Use _ or -. A space turns into %20 and looks broken.
• One source name per platform. Not fb, facebook and Facebook.com in the same month.
• Campaign names that match the ad platform. That way you can join GA4 data to cost data.
• Never put personal data in UTMs. No email addresses or names.

Step 3: Build the link

The easiest tool is Google's Campaign URL Builder for GA4 at ga-dev-tools.web.app/ga4/campaign-url-builder/.

1. Enter the website URL, such as https://example.com/offers/.
2. Fill in campaign source, campaign medium and campaign name.
3. Add campaign content if you have several links in one email or ad.
4. Copy the generated URL at the bottom.

Figure 1. Fill in the fields, then copy the generated link. Illustration of the screen. Labels can differ slightly in your account.

1. Source and medium. Medium email matches the Email channel rule.
2. The final URL. Paste it into your email, post or QR code generator.

If your page URL already has a ?, join the UTMs with & instead. The builder handles this for you. If your link goes through a shortener, test the short link to make sure it keeps the parameters.

For anything beyond a few links, use a shared spreadsheet with dropdowns for source and medium. A simple formula joins the parts:

=A2&IF(ISNUMBER(SEARCH("?",A2)),"&","?")&"utm_source="&B2&"&utm_medium="&C2&"&utm_campaign="&D2

Step 4: Know where not to use UTMs

UTMs can hurt your data as much as help it.

Internal links. Never add UTMs to links from one page of your site to another, such as a homepage banner. When a visitor clicks it, GA4 records a new traffic source mid-visit and overwrites the real one. Use an event or utm-free tracking (like a click event in GTM) for internal promotions.

Google Ads. Keep auto-tagging on in Google Ads. It adds a gclid parameter that gives GA4 richer data, such as campaign, ad group and keyword. You don't need manual UTMs for Google Ads. If you use both, Google's data from auto-tagging normally takes priority.

Other ad platforms. Many platforms support dynamic UTMs, such as a placeholder for campaign name. Google recommends using them where available, so names stay in sync automatically.

Figure 2. Leave auto-tagging on. It does the job of UTMs for Google Ads, with more detail. Illustration of the screen. Labels can differ slightly in your account.

1. Auto-tagging. The exact label may vary, but it lives in account settings.

Step 5: Find and fix "Unassigned"

Now audit what's already happening.

1. In GA4, open Reports > Acquisition > Traffic acquisition.
2. The default table shows Session primary channel group. Find the Unassigned row.
3. Click the dimension dropdown and switch to Session source / medium. Or add it as a secondary dimension with the + button.
4. Filter for the rows that sat in Unassigned. Look for odd mediums.

Figure 3. Unassigned rows usually reveal mediums GA4 doesn't recognize. Illustration of the screen. Labels can differ slightly in your account.

1. newsletter / newsletter matches no rule. Changing the medium to email puts it in the Email channel.

Common patterns and what to do:

What you see	Why it's Unassigned	Fix for future links
newsletter / newsletter	Neither value is email	Use utm_medium=email
flyer / qr	No print or QR channel exists	Use referral, or map qr in a custom channel group
Instagram / Story	Capitalized source may still match, but Story isn't a known medium	Use instagram / social
partner / partnership	Medium unknown	Use referral or affiliate
(not set) / (not set)	Events with no session source, for example sent without a session_start, server-side, or by the Measurement Protocol	Check how those events are sent. Make sure they carry session data

You can't rewrite past data with UTMs. Past sessions stay where they were. Two options help with history:

Custom channel group. Go to Admin > Data display > Channel groups. Click Create new channel group. Copy the default rules, then add a channel such as "Print / QR" with the condition "Session medium exactly matches qr". Move it above the fallback rules. Custom channel groups apply to past data in reports, which makes them a good fix for history. A standard property allows two custom channel groups, so plan them well.

Figure 4. A custom channel group can place your own mediums in a named channel. Illustration of the screen. Labels can differ slightly in your account.

1. Your new channel, placed early so it's checked first. Labels shown are simplified.
2. Save, then pick this group in the Traffic acquisition dimension menu.

Fix the links going forward. Update templates in your email tool, social schedulers and QR codes. Then retire the bad values.

Still not working? Common causes

Symptom	Likely cause	Fix
UTM traffic appears as Direct	Redirect or shortener strips the query string	Test the final URL. Fix the redirect or use another shortener
Campaign shows (not set)	Only source and medium set, or a typo like utm_campain	Set all three. Copy from the builder, don't type by hand
Same campaign split into two rows	Mixed case or spacing (Spring_Sale vs spring_sale)	Lowercase everything. Enforce dropdowns in the sheet
Paid social lands in Organic Social	Medium social used for paid ads	Use paid_social or cpc for ads
Paid social lands in Paid Other	Source isn't in Google's social list (for example fb_ads)	Use a plain platform name like facebook
Sessions jump to a new source mid-visit	UTMs on internal links	Remove them. Use events for internal banners
Google Ads traffic shows as google / organic or Unassigned	Auto-tagging off, or gclid stripped by the site	Turn auto-tagging on. Make sure the site keeps the gclid parameter
Unassigned keeps growing with no UTMs involved	Events without session data (server-side, Measurement Protocol) or consent-related gaps	Check those integrations. See Consent Mode v2
Email clicks all show as Direct	Email app opens links in a way that drops referrer and you sent no UTMs	Tag every email link

How to confirm it's fixed

1. Click your own link in a private browser window.
2. Open Realtime in GA4. In the First user source or session source cards (card names may vary), you should see your source within a minute or two.
3. Check the URL on arrival. The utm_ parameters should still be there after any redirect.
4. Wait 24 to 48 hours, then open Traffic acquisition with Session source / medium. Your values should appear exactly as written, lowercase, in the right channel.
5. Review Unassigned monthly. New team members and new tools tend to reintroduce bad values.

Figure 5. Your test click should show your exact source and medium within a couple of minutes. Illustration of the screen. Labels can differ slightly in your account.

1. Your test visit, spelled exactly as in the link.

For cross-domain journeys where the source gets lost between your own sites, see the cross-domain guide. For counting what those visits achieve, see GA4 key events.

FAQ

Are UTM parameters case sensitive in GA4?

The values are. utm_source=Google and utm_source=google appear as separate rows. Default channel rules ignore case, but your reports will still split. Use lowercase.

Do UTM parameters affect SEO?

Not when used on external links like emails and ads. Keep a canonical tag on your pages so any shared UTM URL points to the clean version. Don't use UTMs on internal links.

Should I add UTMs to Google Ads?

No. Keep auto-tagging on. It sends more detail than UTMs can.

What's the difference between Direct and Unassigned?

Direct means GA4 found no source at all. Unassigned means a source exists but no channel rule matched it, or session data was missing.

Can I fix old Unassigned data?

Not by changing links. A custom channel group can relabel past sessions in reports, as long as the medium or source tells you what they were.

Stuck on this one? We fix these for clients every week. Book a free audit

Sources

• support.google.com: /analytics/answer/10917952
• support.google.com: /analytics/answer/9756891
• ga-dev-tools.web.app: /ga4/campaign-url-builder/
• support.google.com: /analytics/answer/13051316
• web.utm.io: /blog/utm_medium-utm_campaign-utm_source/