What is Source and Medium in Google Analytics?

If you've spent any time in Google Analytics, you’ve probably seen the terms "Source" and "Medium" pop up in your reports. They're everywhere, but it's not always obvious what they mean or, more importantly, what you’re supposed to do with them. Getting a handle on these two simple dimensions is the first big step toward understanding where your website traffic actually comes from and which of your marketing efforts are paying off.

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This article will break down exactly what Source and Medium are, where to find them in Google Analytics 4, and how you can use them to make smarter marketing decisions. We'll even cover how to take control of this data yourself using something called UTM parameters.

What Exactly Are Source and Medium?

Think about how you’d describe a trip you took. If someone asked how you got to the office this morning, you might say, "I drove from my house." In that sentence, "my house" is the starting point (the source) and "drove" is the method of travel (the medium).

That’s exactly how Source and Medium work in Google Analytics. They are a pair of dimensions that work together to describe your website traffic:

• Source: This is the origin of your traffic - the specific website or platform that sent the visitor to you. It answers the question, "Where did this user come from?"
• Medium: This is the category or type of traffic. It answers the question, "How did this user get here?"

When you see them in Google Analytics, they are almost always shown together as a pair, like source / medium. This combination gives you the complete story.

Breaking Down "Source"

The Source is the brand name of the place sending you traffic. Its job is to be specific.

Common examples of sources you’ll see include:

• google: Traffic that came from Google search.
• facebook.com: Traffic that originated from a link on Facebook.
• bing: Traffic that came from the Bing search engine.
• (direct): This represents traffic where the source is unknown or wasn't passed along (more on this later).
• t.co: This is Twitter's link shortener, so it means traffic from X/Twitter.
• yourmonthlynewsletter: A custom source you might create for an email campaign.

Breaking Down "Medium"

The Medium is much broader. It's the general marketing channel or method used.

Common examples of mediums you'll see include:

• organic: Unpaid traffic from search engines like Google or Bing. This is SEO traffic.
• cpc: "Cost Per Click" traffic, which usually means paid ads from platforms like Google Ads or Facebook Ads.
• referral: Traffic that came from a link on another website (that isn't a search engine or a known social platform).
• email: Traffic that came from clicking a link in an email.
• (none): This is paired with "(direct)" source for traffic that has no tracking information.
• social: Traffic from social media platforms. Sometimes this appears, although often GA4 classifies it more specifically as a referral.

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Why You Can't Ignore Source/Medium Data

This information is more than just a list of websites, it's the foundation for attributing your successes and failures. By regularly checking your Source/Medium report, you can gain incredible insight into your marketing performance.

Identify Your Best Performing Channels

It’s one thing to see a lot of traffic from Facebook, but it’s another thing entirely to know if that traffic is actually valuable. By looking at Source/Medium alongside conversion data, you can see which channels are driving the most sales, sign-ups, or leads. Maybe you discover that google / organic brings double the conversions of google / cpc, telling you that your SEO efforts are delivering a better ROI than your paid ads.

Spot Hidden Opportunities

Let's say you see a new Source/Medium pair pop up in your report, like some-niche-blog.com / referral. You notice that even though this blog only sends you 20 visitors a month, half of them convert. That’s a powerful sign that this blog’s audience is a perfect match for your business. You could reach out to them for a formal partnership, a guest post, or an advertising deal.

Diagnose Problems and Underperformance

Did website sales suddenly dip last week? The Source/Medium report is one of the first places to look. You might discover that traffic from facebook / cpc completely dropped off, which could mean your ad campaign was accidentally paused or a new creative isn't performing well. Without this data, you'd be guessing in the dark.

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How to Find and Read the Source/Medium Report in GA4

Finding this report in Google Analytics 4 is straightforward once you know where to click. The main traffic report is designed to give you a channel-level overview first, but you can easily drill down.

Here’s how to get there:

1. Log in to your Google Analytics 4 property.
2. In the left-hand navigation menu, go to Reports.
3. Under the "Life cycle" section, find and click on Acquisition.
4. Click on Traffic acquisition.

By default, GA4 shows you a report based on the "Session default channel group." This is a high-level view (e.g., Organic Search, Direct, Referral). To see the more granular Source/Medium data, you just need to change the primary dimension.

Above the data table, you'll see a dropdown menu that says "Session default channel group." Click this dropdown and search for or select Session source / medium. And there you have it! The report will now display all your traffic broken down by each specific Source/Medium combination.

A Guide to Common Source/Medium Combinations

When you first look at the report, you’ll see many different combinations. Here’s a quick reference for decoding the most common ones you'll encounter:

• google / organic: This is a sign of healthy SEO. It means people are clicking on your website from Google's unpaid search results.
• google / cpc: This is your Google Ads traffic. These are paid clicks from your search campaigns, shopping ads, or Performance Max.
• (direct) / (none): This is mission control for untraceable traffic. "Direct" traffic is often attributed to users typing your URL directly into their browser or using a bookmark. However, it’s also a catch-all bucket for traffic where the referral data is missing, which can happen with clicks from email clients, mobile apps, or shortened URLs that strip tracking info.
• bing / organic or duckduckgo / organic: Traffic from other search engines. It's easy to forget about them, but they can still be a valuable source of users.
• facebook.com / referral or t.co / referral: This is organic traffic from social media platforms. Someone clicked a link in a profile, post, or comment that you did not pay to promote.
• linkedin.com / referral: Traffic from LinkedIn, usually from organic posts or profile links.
• newsletter_may / email: This is perfectly tagged email marketing traffic. The source and medium tell you which campaign it came from and which channel was used.

Taking Control of Your Data with UTM Parameters

Sometimes Google makes its best guess, but you can remove that guesswork entirely by using UTM parameters. UTMs are simple tags you add to the end of your URLs to tell Google Analytics precisely how to categorize the traffic that clicks on them.

What Are UTMs?

UTM stands for "Urchin Tracking Module," which is a throwback to the company Google acquired to create Google Analytics. These "tags" are just snippets of text added after a question mark in your URL. The three most important ones are:

• utm_source: Overrides the default source. (e.g., utm_source=facebook)
• utm_medium: Overrides the default medium. (e.g., utm_medium=cpc)
• utm_campaign: Names the specific marketing campaign. (e.g., utm_campaign=summer_sale_2024)

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A Practical Example

Imagine you're running a paid ad on Facebook for a summer sale. Without UTMs, the traffic might show up as facebook.com / referral or something even less helpful. You won't know if it came from your paid campaign or a regular post.

Instead, you build a custom URL. Let's say your landing page is:

https://www.yourshop.com/summer-sale

You can add your UTM tags like this:

https://www.yourshop.com/summer-sale?utm_source=facebook&utm_medium=paid_social&utm_campaign=summer_sale_ad

Now, anyone who clicks that specific link in your ad will appear in your GA4 report with the source set to facebook, the medium set to paid_social, and the campaign set to summer_sale_ad. You have perfect, clean data that tells you exactly how your campaign is performing.

Tips for Clean UTM Tagging

• Be Consistent: Always use lowercase letters. facebook and Facebook are treated as two different sources in your reports, so stick with one convention.
• Use Underscores (or Dashes): Don't use spaces in your parameters. Use summer_sale instead of summer sale.
• Keep a Record: Use a simple Google Sheet or spreadsheet to track the UTMs you create for each campaign. This ensures everyone on your team uses the same conventions.
• Use a Builder Tool: You don't have to manually type these every time. Google's free Campaign URL Builder makes it easy to generate these links without mistakes.

Final Thoughts

Understanding the difference between Source and Medium is fundamental for any marketer, business owner, or creator. It’s what transforms Google Analytics from a confusing sea of numbers into a powerful tool for measuring what works, what doesn't, and where your most valuable customers come from. By mastering this report and taking control of your data with UTMs, you'll be well on your way to making data-informed decisions that truly grow your business.

The real challenge often begins after you've found your best-performing channels in Google Analytics. How do you tie that google / cpc traffic directly to revenue in your Shopify store, or connect that linkedin / referral traffic to closed deals in Salesforce? We built Graphed to eliminate the hours of manual work it takes to connect these dots. Instead of exporting CSVs and fighting with spreadsheets, you can hook all your platforms into one place and just ask a simple question like, "Show me which Facebook campaigns and sources generated the most sales last month," and get an instant, real-time dashboard that answers your question in seconds.