How Google Analytics Identifies Traffic Sources — or Why You Have So Much Direct Traffic

In web analytics, one of the most common challenges is understanding which marketing channels actually pay off. You launch ads on Facebook, send out email newsletters, post updates on LinkedIn — but how can you see what exactly brought visitors and which channels performed better? If your traffic lacks proper breakdown, you get numbers but miss the key element — clear context: which source truly works and delivers results.

Of course, Google Analytics has its own algorithms for identifying sources and, even without your intervention, tries to classify traffic. But here lies the main problem: without your help, you leave Google Analytics to sort out all this information on its own — and often end up with a significant portion of traffic categorized as “direct/none,” which is impossible to work with because it’s unclear what it actually represents. This is exactly the problem that UTM tags solve.

UTM tags are small technical parameters in a URL that make a big difference for your analytics. And in this article, we’ll break them down in detail.

• What Are UTM Tags
  • Technical Features of UTM Tags
  • Business Features of UTM Tags
• How Google Analytics 4 Identifies Traffic Sources (and Why UTM Tags Are So Important)
  • What Is a Traffic Source
  • How GA4 Identifies Source and Medium of Traffic
• How to Properly Use and Format UTM Tags
  • Structure of UTM Tagging
  • Why utm_term and utm_content Don’t Have Clear Rules Like the First Three Tags
  • How to Use Google’s Campaign URL Builder
  • Key Rules for Filling Out UTM Tags
• How to Create a Custom UTM Tag Template for Your Team
• Conclusion
• FAQ
  • Can You Use UTM Tags Together With Google Ads Auto-Tagging?
  • Do UTM Tags Affect SEO and Website Ranking?
  • Can You Use UTM Tags on Internal Website Links?
  • Is Case Sensitivity Important for UTM Tags?
  • Can You Use Cyrillic in UTM Tags?
  • Should You Use UTM Tags for Email Campaigns?
  • Can You Edit UTM Tags After Launching a Campaign?
  • Do UTM Tags Affect Page Loading Speed?
  • What Are utm_id and utm_source_platform?
  • Can You Use Spaces in UTM Parameters?
  • How Many Characters Can Be Used in UTM Tags?
  • Can You Add Personal Data (Email, Phone) to UTM Tags?
  • Where Is the Easiest Place to Create UTM Tags?

What Are UTM Tags

Like most important concepts in web analytics, UTM tags combine two contexts: business and technical. We’ll look at both — starting with the latter.

Technical Features of UTM Tags

Technically, UTM tags are GET parameters in your URL. What are GET parameters? They are pairs of “name=value” added to your website’s URL after a question mark.

Here’s an example of a regular website link:

https://proanalytics.academy/

And here’s the same link with UTM tags:

https://proanalytics.academy/?utm_source=instagram&utm_medium=cpc

In the structure of this link, we can see two “name=value” pairs: utm_source=instagram and utm_medium=cpc. Typically, there are at least five such pairs used, but for now, we’ll focus on these two.

What makes these pairs so special? The main advantage is that UTM tags simultaneously send information about the traffic source to Google Analytics while not affecting the content of your website.

Try opening both links above — you’ll notice the content is exactly the same. However, in the first case (without UTM), Google Analytics 4 will register the visit as direct/none, while in the second case — as instagram/cpc.

Website without UTM tags:

Website with UTM tag:

Business Features of UTM Tags

If you’re reading this material, most likely you or your colleagues run various marketing activities daily — in newsletters, social media, or partner platforms. And if you want to know which of these actions brings results and which don’t — before inserting a link into an ad account, email, or post — make sure to tag it with UTM parameters. Yes, I’ll repeat this point in several forms throughout this article so it sticks well in your mind.

Now, back to the business features: these tags are a critical part of the work of analysts, marketers, and PPC specialists. To understand why, let’s see how Google Analytics 4 determines the source and medium of traffic.

How Google Analytics 4 Identifies Traffic Sources (and Why UTM Tags Are So Important)

What Is a Traffic Source

One of the main goals of web analytics is to analyze traffic effectiveness. In GA4, there are built-in system parameters for this:

• Source — the platform that brought the traffic, for example, Facebook, Google, eSputnik.
• Medium — the method of acquiring that traffic, for example, CPC (paid advertising), organic (unpaid traffic organically coming from search engines), email, etc.

For example, in Google Analytics 4, this might look like:

• google / cpc — paid traffic from Google Ads;
• google / organic — organic traffic from Google;
• esputnik / email — traffic from an email newsletter;
• bing / organic — organic traffic from Bing;
• l.facebook.com / referral — free traffic from Facebook, coming through mentions by other people;
• (direct) / (none) — direct traffic, meaning the traffic GA4 was unable to identify.

How GA4 Identifies Source and Medium of Traffic

To determine the traffic source and medium, Google Analytics 4 follows a sequence of rules. It works like a “cascade”: the system first tries to apply one rule, and if it doesn’t fit, it moves to the next one — and continues until it finds data suitable for classification.

1. Google Ads Auto-Tagging (GCLID, GBRAID, WBRAID, etc.)
   The first thing GA4 looks for is a special Google Ads auto-tag (GCLID, GBRAID, WBRAID, or their equivalents). When you run ads through Google Ads and enable auto-tagging, special GET parameters are added to your URLs. These contain data about the ad click (and other relevant Google Ads details). If this auto-tag is present, Google automatically classifies the source as google and the medium as cpc (meaning paid Google advertising). In your reports, this appears as google / cpc, ensuring accurate classification of paid traffic coming from Google Ads.
2. UTM Tags.
   If no auto-tag is found, GA4 checks whether your link contains UTM parameters. If they are present, the system assigns the source and medium based on the values you defined manually — for example, facebook / cpc, esputnik / email, forbes / banner, etc. This is the most controlled and transparent way to define traffic sources — you decide how the traffic will be classified and get the exact level of detail you need.
3. Referrer (Previous Domain).
   If there’s no auto-tag or UTM parameters, Google turns to the so-called document.referrer — the domain of the website from which the user came to your site (technically, it’s a bit more complex, but we’ll simplify it here). For example, if I posted a link to your site on my blog analytics-tips.com, Google would record that traffic as referral, more precisely as analytics-tips.com / referral, because the referring page contains information about the source of the visit.

Note: Some referrers are recognized by Google in a special way — if the referring domain is a search engine, it’s classified as organic (organic search traffic).

4. (direct) / (none) — direct, or more accurately, “unknown” traffic.

If none of the previous three checks return a match, Google records the visit as direct / none. Formally, this means the user supposedly entered your site’s address manually or used a bookmark.

But by now you understand that, in reality, this simply means there was no Google Ads auto-tag, no UTM parameters, and no value in “document.referrer.”

And this brings us to an important conclusion:

Or in other words:

How to Properly Use and Format UTM Tags

Structure of UTM Tagging

As mentioned earlier, there are typically five UTM tag pairs used. Let’s break down each one and understand its role:

• utm_source — the traffic source, meaning the platform or site where you usually invest (money or time) to attract users to your website. Examples: facebook, google, linkedin, esputnik, youtube.
• utm_medium — the channel through which the traffic was acquired. It shows what you pay the platform for: cpc — cost per click (paid ads), email — for sent newsletters, banner — for display ads, etc. There’s one conditional exception — social. This channel is used to indicate free traffic from your own social media pages. In other words, that’s when you “paid with time.” :)
• utm_campaign — the name of the marketing campaign that ties all your activities into one cohesive story. Examples: black_friday, new_year, spring_sale.

Important: If you run multiple activities under the same marketing campaign — for example, on Black Friday you launch ads on Facebook, post promotions on Instagram, and send an email newsletter — don’t name each one separately (“email_black_friday,” “instagram_black_friday,” “facebook_black_friday”).

A single campaign name, like black_friday, is enough for all channels.

If the first three pairs have general naming rules, the next two usually depend on the platform that helps attract traffic. Let’s look at some examples to make it clearer.

• utm_term — an auxiliary variable where you can enter a keyword, ad group, mailing list segment, or blogger nickname.
• utm_content — provides even greater detail: the name of a banner, email, creative, specific video, or particular ad. For example, in an email campaign, utm_content can help track which email performed better — the early announcement or the final sale-day reminder. In a banner campaign, it helps distinguish between different formats or versions of a banner.

Examples of tagging:

For paid Facebook ads:

• utm_source=facebook
• utm_medium=cpc
• utm_campaign=black_friday
• utm_term={{ad_group_name}}
• utm_content={{ad_name}}

For email campaigns sent via eSputnik:

• utm_source=esputnik
• utm_medium=email
• utm_campaign=black_friday
• utm_term={{contact_group_name}}
• utm_content={{email_name}}

Why utm_term and utm_content Don’t Have Strict Rules Like the First Three

Originally, utm_term and utm_content fields were used specifically for passing keywords and ad names in Google Ads. But over time, UTM tags became an industry standard, and their use expanded across all systems. The first three tags were easy to adapt, but utm_term and utm_content didn’t always have direct equivalents. Still, marketers wanted more detail — so they simply started filling them with whatever information they needed.

Today, these are universal variables where you can “store” anything that helps with deeper analytics — from ad group names to creative details. If you want to see which creative, ad group, email, or {{insert your value}} performs better, you can’t do without them.

To summarize everything we’ve learned so far, I suggest reinforcing it by reviewing the final UTM tagging diagram — it’ll help you visualize the concept more clearly.

How to Use Google’s Campaign URL Builder

Properly constructing a UTM-tagged link is an important — and not always easy — task. To help users avoid syntax mistakes, Google created Campaign URL Builder — a handy web interface where you paste your link, fill in the tag fields, and instantly get a ready-to-use, error-free URL.

Google recommends filling in at least three tags: utm_source, utm_medium, and utm_campaign. However, I suggest including all five. Let’s look at an example for Facebook ads:

1. Paste your website URL.
2. Enter utm_source: “facebook”.
3. Enter utm_medium: “cpc”.
4. Enter utm_campaign: “black_friday”.
5. Add utm_term: “bf_main_group” (ad group name).
6. Add utm_content: “big_discount_banner” (ad name).

Below, the system immediately generates a complete URL that you can copy — simple and error-free.

As you can see, using Campaign URL Builder makes the process quite straightforward. But even in such seemingly simple actions, there are several nuances that can completely ruin your analytics.

To avoid common mistakes and confusion, let’s go over the key rules for filling out UTM tags that help keep your data clean, clear, and well-structured across all campaigns.

Key Rules for Filling Out UTM Tags

In UTM tagging, there are real “rules of good manners.” These determine whether your web analytics will stay understandable — or turn into chaos.

• Keep your naming clean.
  • For utm_source and utm_medium, use only lowercase Latin letters, numbers, and underscores.
  • Avoid spaces, Cyrillic characters, and special symbols (?, &, #).
  • Don’t write “Facebook Ads” — the correct format is “facebook.”
• Be unambiguous.
  • Choose tag names that would make sense even to someone outside your team.
  • Avoid vague abbreviations like utm_source=g.
• Use Campaign URL Builder. It helps you follow proper URL structure:
  • UTM parameters are added after “?”, and each subsequent parameter is separated by “&”.
• Don’t make tags too long.
  • The shorter and clearer your URL, the lower the risk that something will “break” in your analytics or CRM.
• Don’t include sensitive data.
  • Never insert emails, phone numbers, or personal data into tags — for both security and GDPR compliance reasons.
• Use UTM tags only for external traffic.
  • Internal website links should never be tagged with UTM — this will mess up your analytics and create unnecessary “noise.”
• Document and align.
  • Your company should have a document describing the general logic of UTM tagging, with regularly updated examples.
  • It’s best to have a shared template for every new campaign — so your team can reference it and always keep your GA4 data tidy and consistent.

How to Create a UTM Tag Template for Your Team

Once you have several channels and multiple team members working on campaigns, “tag mixing” inevitably starts. To prevent chaos, most projects create a UTM tagging template — a document or spreadsheet that outlines which specific values each tag should have for every marketing activity.

What your template should include:

1. Clearly defined parameters for each channel or activity.
   1. Example for an email campaign:
      1. utm_source=esputnik
      2. utm_medium=email
      3. utm_campaign={campaign_name}
      4. utm_term={contact_group_name}
      5. utm_content={email_name}
2. Explanations for dynamic fields with correct examples.
   1. {contact_group_name} — name of the contact group as it appears in the eSputnik interface; use only Latin letters and replace spaces with underscores. Example: proanalytics_students.
   2. {email_name} — internal name of the email in eSputnik, following a consistent format (newsletter_{mailing_number}, e.g., newsletter_048, newsletter_050, etc.).
3. Agreed-upon template usage rules within your marketing team.

Conclusion

I hope you now understand how important it is to create UTM tagging — and, most importantly, how to do it correctly.

This seemingly small step actually opens up huge opportunities for your business: it helps you stop guessing where your traffic comes from and start clearly understanding the performance of every campaign, channel, or creative.

Don’t forget to follow the rules, align them with your team, and keep updating your template with real examples — that way, you’ll always have a complete and accurate picture of what’s happening with your traffic.

That means fewer guesses, more precision, and marketing that truly delivers measurable results.

By the way, there are more UTM parameters than just the basic five. Additional ones, such as utm_id, utm_platform, and others, also exist. They may be useful for more advanced projects — but if you’re just starting to build your analytics system, the five main parameters will be more than enough for most cases.

FAQ

Can You Use UTM Tags Together With Google Ads Auto-Tagging?

Yes. Auto-tagging can only be read by Google services, while CRMs, call-tracking systems, and other similar tools rely solely on UTM parameters. By using UTM tags together with Google Ads auto-tagging, you provide the maximum amount of information to all systems.

Do UTM Tags Affect SEO and Website Ranking?

UTM tags themselves don’t affect ranking, but for Google, they represent separate pages — and if not optimized, they can be indexed and create duplicates.

To avoid this, configure a canonical tag pointing to the main page or use meta noindex for such URLs.

Can You Use UTM Tags on Internal Website Links?

No! This is one of the most common mistakes. Adding UTM parameters to internal links will mess up attribution and create fake traffic sources in your reports.

Is Case Sensitivity Important for UTM Tags?

Yes. Google Analytics treats “Facebook” and “facebook” as two different sources. Always use a consistent format (preferably lowercase). Ideally, your team should have clear internal rules for UTM naming conventions.

Can You Use Cyrillic in UTM Tags?

Technically yes, but it’s a bad practice. Cyrillic characters may break in some systems, so it’s always best to use Latin letters.

Should You Use UTM Tags for Email Campaigns?

Yes. Email clients often don’t pass a referrer, so without UTMs, your email traffic will appear as (direct) / (none).

Can You Edit UTM Tags After Launching a Campaign?

Technically yes, but it’s a bad idea. Changing tags after launch will distort your analytics. Always test your links before going live.

Do UTM Tags Affect Page Loading Speed?

No, they don’t impact site performance. They’re simply parameters in the URL that analytics tools read.

What Are utm_id and utm_source_platform?

These are additional parameters for advanced GA4 analytics. They allow for deeper campaign identification but aren’t required for beginners. More details are here.

Can You Use Spaces in UTM Parameters?

No. Replace spaces with underscores (_) or hyphens (-). Otherwise, the URL may break.

How Many Characters Can Be Used in UTM Tags?

There’s no strict technical limit, but overly long URLs can break in some systems. Keep your parameters concise and readable.

Can You Add Personal Data (Email, Phone) to UTM Tags?

Absolutely not. It’s a violation of GDPR and security policies. Never include personal data in URLs.

Where Is the Easiest Place to Create UTM Tags?

Use Google Campaign URL Builder — it’s a free and simple tool that helps you avoid syntax mistakes.