Guide · Beginner
UTM Parameters and Attribution Basics
UTM parameters are tags you add to the end of a link, such as `?utm_source=newsletter&utm_medium=email&utm_campaign=spring_sale`. They tell analytics tools where a visit came from. Attribution is how credit for a sale or sign-up is shared between the touchpoints that led to it. Get UTMs right and your channel reports become reliable. Get them wrong and the same campaign shows up as five different sources.
Facts are from Google Analytics Help pages, checked on 31 Oct 2026 (CET). Examples are illustrative. "Our view" marks opinion.
On this page
- What are UTM parameters?
- How do you build a tagged link?
- What naming rules keep data clean?
- When should you not use UTMs?
- What is attribution?
- How does AI assistant traffic fit in?
- Quick checklist
- Where next?
- From MentionX data: why AI referrals are hard to attribute
- Worked example: Ledgerline cleans up its campaign tagging
- What are the five UTM parameters?
- How do UTMs show up in Google Analytics 4?
- How do you share naming rules?
- How do you audit existing tagging?
- How do you handle links in AI answers?
- What about privacy?
- Which attribution model should a beginner use?
- How do you explain attribution to stakeholders?
- How do you test a tagged link?
- How do UTMs work with short links?
- How should small teams start?
- Common questions
- Sources
Checked on 31 October 2026. "Our view" marks MentionX opinion. Ledgerline is a fictional company used for illustration.
What are UTM parameters?
They're name-value pairs added to a destination URL. When someone clicks the link, Google Analytics reads the values and shows them in the Traffic acquisition report (Google). Google lists these parameters (Google):
| Parameter | What it records | Example |
|---|---|---|
| utm_source | The referrer | newsletter, linkedin |
| utm_medium | The marketing medium | email, cpc, social |
| utm_campaign | The campaign, product or promotion | spring_sale |
| utm_content | Which creative or link | header_button |
| utm_term | Paid keyword | crm_software |
| utm_id | Campaign ID | spring26 |
Google also lists utm_source_platform, utm_creative_format and utm_marketing_tactic, and notes that the last two aren't currently reported in Google Analytics (Google).
Google says you should always use utm_source, utm_medium and utm_campaign (Google).
How do you build a tagged link?
Fictional example: your spring newsletter links to a pricing page.
https://www.example.com/pricing?utm_source=newsletter&utm_medium=email&utm_campaign=spring_sale&utm_content=hero_button
In GA4 this visit appears with source "newsletter" and medium "email", grouped under the email channel. You can use Google's URL builder or a shared spreadsheet to create links (Google).
What naming rules keep data clean?
Google recommends a standard UTM strategy across all marketing so data isn't split up, and so channel groups classify traffic correctly (Google). In practice:
- Use lowercase everywhere. "Email" and "email" can show up as separate values.
- Use one source name per platform. Decide on "linkedin" or "li", not both.
- Use standard mediums such as email, cpc, social and referral, so GA4's default channel group sorts traffic correctly.
- Use underscores or hyphens, never spaces.
- Keep a shared log of every tagged link, with the date and owner.
Our view: a one-page naming guide and a shared link builder sheet prevent most problems.
When should you not use UTMs?
- On internal links. A UTM on a link from your homepage to your pricing page restarts the visit's source and wipes out where the visitor really came from.
- On links you don't control, such as links in AI answers or on review sites. Measure these by referrer instead.
- On canonical URLs. Keep tagged links for campaigns and make sure the page's canonical is the clean URL. See canonicals and duplicates.
What is attribution?
Most buyers interact with you several times before converting. Attribution decides how credit is shared:
| Model | How credit is assigned |
|---|---|
| Last click | All credit to the final touchpoint |
| First click | All credit to the first touchpoint |
| Data-driven | Credit shared based on how touchpoints actually contribute |
GA4's Attribution reports offer three models: data-driven attribution, paid and organic last click, and Google paid channels last click (Google). Google says data-driven attribution uses your account's data and machine learning to work out how much each click interaction contributes, looking at both converting and non-converting paths (Google). Note one detail that matters for AI traffic: Google says all of these models exclude direct visits from attribution credit, unless the path consists entirely of direct visits (Google). So AI-driven visits that arrive without a referrer and land in direct get no credit in these reports.
GA4 lets you mark important actions as key events and use its attribution and pathing reports to see how credit is shared across touchpoints (Google). See GA4 basics.
Fictional example: a buyer reads a LinkedIn post, later asks ChatGPT for recommendations and clicks through to your site, then returns through a newsletter link and signs up. Last-click gives all the credit to the newsletter. The earlier touchpoints influenced the decision but receive none.
How does AI assistant traffic fit in?
You don't control the links AI assistants show, so you can't rely on UTMs. Instead, group visits by referrer. Google's help page on custom channel groups gives an "AI assistants" example: a channel matching referrer sources such as ChatGPT, Gemini, Copilot, Claude and Perplexity with a regular expression (Google). Custom channel groups can be applied to reports retroactively (Google). See the GA4 custom channel group for AI referrals.
Some AI-driven visits arrive without a referrer and show as direct traffic. That's why AI referral numbers are usually a lower bound. See why AI referral traffic is undercounted. Adding "How did you hear about us?" to forms helps fill the gap. See self-reported attribution.
Quick checklist
- Every campaign link has source, medium and campaign
- Values are lowercase and follow the naming guide
- No UTMs on internal links
- Key events are set up in GA4
- An AI assistants channel exists in a custom channel group
- Forms ask how people heard about you
Where next?
Read tracking AI traffic in GA4 and attribution from AI visibility to pipeline.
From MentionX data: why AI referrals are hard to attribute
Method. Read-only aggregate queries over MentionX scans from 22 August to 29 October 2026 (UTC): 2,217 engine runs (2,154 completed) across 18 anonymised projects and six engines.
Many AI answers include no links at all, which means no click and no referral to tag or measure. In the MentionX sample, the share of answers with no citations varied widely by engine:
| Engine | Brand mentioned | Answers with no citations |
|---|---|---|
| Gemini | 47.3% | 50.7% |
| OpenAI | 42.9% | 30.2% |
| Perplexity | 31.5% | 4.1% |
| AI Mode | 31.3% | 12.6% |
| Copilot | 26.0% | 47.0% |
| DeepSeek | 24.0% | 99.0% |
Where citations do appear, they point to a range of page types:
| Cited URL type | Share of 9,750 citations |
|---|---|
| Blog or article | 19.6% |
| Homepage | 10.0% |
| Review page | 2.7% |
| Docs | 2.6% |
| Pricing | 1.9% |
| Wikipedia | 1.6% |
Our view: UTMs only help with links you create. AI assistant traffic arrives through links the engine chose, so track it with referrer data and self-reported attribution, and measure mentions separately.
Limits. A convenience sample of mostly B2B software projects, run through engine APIs, which can behave differently from the consumer apps. Perplexity, Copilot and DeepSeek figures come from a single day (26 October 2026), so treat them as a snapshot, not a trend.
Worked example: Ledgerline cleans up its campaign tagging
Ledgerline is a fictional accounts-payable tool. Figures are illustrative.
Ledgerline's analytics show the same newsletter under five different sources: "Newsletter", "newsletter", "email", "mail" and "nl". The marketing team can't tell how much traffic email really brings.
The marketing operations lead writes a one-page naming guide: all lower case, a fixed list of sources and mediums and a campaign format with the year and month. She builds a shared link builder in a spreadsheet that only allows values from the list. She removes UTMs that had been added to internal banner links, which were overwriting the original source of visits. A month later, email traffic appears under one source and medium.
What are the five UTM parameters?
There are five standard parameters. utm_source names where the traffic comes from, such as a newsletter or a partner site. utm_medium names the type of channel, such as email, social or paid search. utm_campaign names the campaign. utm_term is mostly used for paid search keywords. utm_content distinguishes between links in the same campaign, such as two buttons in one email. Source, medium and campaign are the ones most teams use every time.
How do UTMs show up in Google Analytics 4?
GA4 reads the parameters and fills in the session source, medium and campaign. These feed default channel groups, such as Email or Paid Social. If your medium doesn't match what GA4 expects, traffic may land in "Unassigned". Check GA4's channel definitions when you choose your medium values.
How do you share naming rules?
Write the rules in one short document with examples, and link to it from wherever people build links. Include a list of approved sources and mediums. Review the list quarterly and remove values nobody uses. Make one person responsible for approving new values.
How do you audit existing tagging?
In GA4, look at the source and medium report for the past few months. Look for near-duplicates, upper-case values and unexpected mediums. List them, agree the correct values and update active links. Old data won't change, so note the date the clean-up happened.
How do you handle links in AI answers?
You can't add UTMs to links that engines generate. Some AI assistants pass a referrer, and some add their own parameters, but behaviour varies and changes. Track known AI referrers in a custom channel group, and add a "How did you hear about us?" question to key forms to capture visits that arrive without a referrer.
What about privacy?
Don't put personal data, such as email addresses or names, in UTM parameters. They appear in URLs, reports and sometimes third-party tools. Use campaign IDs instead.
Which attribution model should a beginner use?
GA4 uses data-driven attribution by default for many reports, and also offers last-click. Data-driven models spread credit across touchpoints based on your data; last-click gives all credit to the final source. Neither is perfect. Our view: beginners should use the default, understand what it does and look at more than one view before drawing conclusions about a channel.
How do you explain attribution to stakeholders?
Explain that attribution is an estimate, not a complete record. Some visits can't be tracked, some buyers use several devices and some influence, such as an AI answer that mentions you without a link, never shows up as a click. Pair attribution reports with other evidence, such as self-reported sources and brand search trends.
How do you test a tagged link?
Before you send a campaign, click the tagged link yourself and check GA4's real-time report. Make sure the source, medium and campaign appear as expected. Check that the link still works after any redirects, because some redirects strip parameters. Test links in emails from several email clients, since some add their own tracking.
How do UTMs work with short links?
Short links are fine as long as the short link points to the full tagged URL. Keep a record of each short link and what it points to. Avoid shortening internal links, which should never carry UTMs anyway.
How should small teams start?
Start with a few sources and mediums that cover your main channels: email, social, partners and paid ads. Tag every external campaign link from now on. Review the data once a month. Add more detail only when you have a question that needs it.
Common questions
Are UTM parameters case-sensitive? Yes, in most analytics tools; use lower case to avoid duplicates.
Should I tag social posts? Yes, for posts you publish, so you can compare them with other channels.
Do UTMs affect SEO? Not when used on external campaign links; avoid them on internal links.
Sources
- Google, URL builders: collect campaign data with custom URLs
- Google, About key events
- Google, Get started with attribution
- Google, Custom channel groups
Questions
Which UTM parameters do I need?
Google recommends always using utm_source, utm_medium and utm_campaign. utm_content and utm_term are optional.
Should I add UTMs to internal links?
No. UTMs are for links from outside your site, such as emails, ads and social posts. On internal links they overwrite the original source of the visit.
Can I put UTMs on links that AI assistants cite?
You can't control the links AI assistants cite to your site. Measure AI assistant traffic by referrer with a GA4 custom channel group instead.