What is Session Medium in Google Analytics 4?

Digging into your Google Analytics 4 data and seeing terms like "Session medium" can feel a little confusing, especially if you're used to Universal Analytics. This simple dimension is one of the most powerful tools you have for understanding how people get to your website for each visit. This article will break down exactly what Session medium means, how it differs from other traffic metrics, and how you can use it to get real, actionable insights about your marketing performance.

What Exactly is 'Session Medium' in GA4?

Think of Session medium as the general category, or "type," of traffic that brought a user to your website for a specific visit. It answers the high-level question: "How did they get here this time?"

An easy way to understand it is to compare it to its partner dimension, "Session source."

• Session Source: This is the specific name of the website or platform that sent the traffic. Examples include "google.com," "facebook.com," or the name of a newsletter ('spring-promo-2024').
• Session Medium: This is the general classification of that source. It buckets those specific sources into broader categories. For example, traffic from "google.com" would fall under the "organic" medium, while traffic from "facebook.com" belongs to the "social" medium.

Together, they provide a full picture. Knowing your Session source is "google.com" is useful, but knowing the Session medium is "organic" tells you they found you through unpaid search results, which informs your SEO strategy. Both pieces are valuable, but the medium gives you the strategic overview of which types of marketing are actually working.

First User Medium vs. Session Medium: A Key Distinction in GA4

One of the most common points of confusion in GA4 is the difference between metrics that start with "First user" and those that start with "Session." Understanding this is crucial for accurate analysis.

First User Medium: The Origin Story

The "First user medium" tells you how a user first discovered your website. This value is assigned to them on their very first visit and (with some technical exceptions) stays with that user for good. It's designed to answer the question: "Which marketing channel was responsible for acquiring this user in the first place?"

This is extremely useful for understanding the long-term value of your acquisition channels. For instance, you can use a "First user medium" report to see if users who originally discovered you via organic search eventually become your most valuable customers, even if they later visit through other channels.

Session Medium: The Current Chapter

The "Session medium," as we've discussed, tells you how a user arrived for their most recent session. This can change with every visit they make. It answers the question: "What brought this user to the site today?"

Let's look at a practical example:

1. Monday: A user searches Google for "best running shoes for trails" and clicks your organic search result to visit your blog for the first time.
2. Friday: You send out your weekly newsletter. That same user sees your email, clicks a link to a product page, and returns to your site.

Both dimensions are correct, they just tell different parts of the customer journey story. Use "First user medium" to analyze long-term channel ROI for customer acquisition and use "Session medium" to assess the real-time performance of your various marketing campaigns and day-to-day traffic drivers.

Where to Find and Use the Session Medium Reports

Finding this critical data in GA4's interface only takes a few clicks. It lives within the main traffic acquisition report, which is your go-to destination for analyzing where your visitors came from.

How to locate the 'Traffic acquisition' report:

1. Navigate to the Reports section (the chart icon) in the left-hand menu.
2. Under the "Life cycle" drop-down, click on Acquisition.
3. Select the Traffic acquisition report.

By default, this report probably shows "Session default channel group" as its primary dimension. This is helpful, but seeing the straight "Session medium" gives you a slightly different, more granular view. To change it:

• Click the small down-arrow on the first column heading of the table.
• In the search box that appears, type "Session medium" and select it.

The table will now reload with "Session medium" as the primary dimension, showing you a clean breakdown of your traffic by these categories, along with key metrics like Users, Sessions, Engaged sessions, and Conversions.

Understanding The Default Mediums in Google Analytics

GA4 automatically categorizes your incoming traffic into several default mediums. Here’s a quick rundown of the most common ones you’ll see and what they mean:

• organic: This is traffic from users who clicked an unpaid link from a recognized search engine like Google, Bing, or DuckDuckGo. This is a direct reflection of your SEO efforts.
• cpc (cost-per-click) / paid: This is traffic from paid advertising where you pay for each click. It most commonly refers to search ads from platforms like Google Ads and Microsoft Ads.
• referral: This refers to traffic that arrived by clicking a link on another website (one that is not a major search engine). Think of links from a guest post you wrote, a media mention, or a partner's website.
• email: As you'd expect, this is traffic from users clicking links within your emails. For this to work accurately, you must be using UTM tracking parameters on your email links.
• (none): This is the medium associated with Direct traffic. It means GA4 has no referral data for the session. The user likely typed your URL directly into their browser, used a bookmark, or clicked a link from a non-web source (like a PDF or a mobile app without tracking).
• social: This medium covers traffic from links on social media platforms, both organic posts and paid ads. The source dimension will tell you whether it was Facebook, LinkedIn, X, etc.
• display: This medium tracks traffic coming from display ads, like banner ads you might run on the Google Display Network or other ad networks.
• (not set): This value isn't a type of traffic, it's an indicator that Google Analytics received a hit but couldn't identify the medium for some reason. It often points to a problem with tracking code implementation or, more commonly, incorrect or missing UTM tracking on a custom campaign URL. You'll want to investigate any significant amount of "(not set)" traffic.

How to Use Session Medium Data for Smarter Marketing

Alright, you know what Session medium is and where to find it. Now for the most important part: using that data to make better decisions.

Identify and Double Down on Your Top-Performing Channels

Sorting your Traffic acquisition report by "Conversions" or "Engaged sessions" immediately shows which mediums are bringing you the most valuable traffic. Is your "organic" medium driving the vast majority of your e-commerce purchases? That's a clear signal to invest more resources into content creation and SEO. Is your "email" medium showing the highest Engagement Rate? That tells you your email list is highly valuable and you should focus on growing it and nurturing those subscribers.

Spot Hidden Opportunities for Growth

Watch for unexpected mediums that are performing well. For example, if you see a healthy amount of converting traffic from the "referral" medium, you'll want to dig deeper. Add "Session source" as a secondary dimension to that report to see which exact websites are sending that traffic. If a single blog mention is sending you high-quality visitors, it is an obvious hint to reach out for a more formal partnership or guest posting opportunity.

Diagnose and Debug Your Campaign Tracking

Your medium report is one of the best places to spot issues with your campaign tagging. If you just launched a major email campaign but see that traffic showing up as "(none)" or "referral" instead of "email," you know your link tracking is broken. This is almost always because the URLs in your email are missing the proper UTM parameters. Specifically, the traffic's medium is pulled directly from the utm_medium tag in the URL. A correctly tagged URL looks like this:

https://www.yourwebsite.com/landing?utm_source=spring-newsletter&utm_medium=email&utm_campaign=20-off-sale

Without utm_medium=email, GA4 has no idea where the click came from and will likely miscategorize it. Consistency here is key to clean, trustworthy data.

Final Thoughts

In short, Session medium is your window into the day-to-day effectiveness of your marketing channels. It strips away the complexity to show you, at a glance, how users are arriving on your site for each visit, providing the clear, high-level context you need to evaluate performance, diagnose tracking issues, and spot new opportunities for growth.

We know that digging through menus and building custom reports in Google Analytics can sometimes feel like a full-time job. We built Graphed to remove that friction completely. Instead of manually creating these reports every week, you can connect your Google Analytics account in seconds and just ask a question in plain English, like, "Show me a chart of my top session mediums by conversions for last month.” Our AI data analyst instantly creates a live dashboard with the answer, updating in real-time, freeing you up to actually focus on strategy instead of report-building.