Have you ever got lost in GA4 data, confused by “Session source / medium” and “First user source / medium”? You are not alone. These two similar-looking dimensions work differently, and they affect how you understand user behaviour and even the marketing decisions you make.
This article unpicks both dimensions step by step so you can see them clearly.
How does GA4 record source / medium?
Source records where users came from, and medium records how they came. GA4 records source / medium in the following ways:
1. Auto-tagging:
- Google Ads: GA4 automatically records traffic from Google Ads as google / cpc or google / cpm.
- Google Search: for organic traffic from Google Search, GA4 automatically sets the source to google and the medium to organic.
2. Manual tagging:
You can tag campaign links manually with UTM parameters, for example in social media posts and email newsletters. GA4 records source / medium from the utm_source and utm_medium parameters.
3. Other sources:
For traffic from other sources, GA4 identifies source / medium as best it can from the HTTP referrer and other information.
What is the difference between session source / medium and first user source / medium in GA4?
Although the names are similar, they track very different things. Session source / medium focuses on current behaviour, while First user source / medium looks at where the user first started.
Say a user first discovers your website through a Facebook ad (First user source / medium), then later returns several times via Google Search (Session source / medium). In this case, the two dimensions will show different results.
How can you use them to improve marketing performance?
Once you understand the difference, you can analyse user behaviour more effectively and improve your marketing strategy:
1. Understand the user journey
-
See how users first found you: First user source / medium shows which channels are most effective at attracting new users, so you can invest more in those channels in future.
-
Analyse what users do next: Session source / medium shows which channels users come back through after they have discovered you, so you can improve your website content and user experience.
2. Evaluate campaign performance
-
Track the impact of specific campaigns: for example, you can set UTM parameters for a Facebook campaign and use Session source / medium to track how many users reached your website through that campaign.
-
Compare return on investment across channels: by comparing the number of users, conversion rates and other metrics from different sources and media, you can allocate your marketing budget more effectively.
FAQ
-
Q: Can I track Session source / medium and First user source / medium at the same time?
-
A: Yes. GA4 offers a wide range of reports and analysis tools that let you track both easily.
-
-
Q: Which dimension is more important?
-
A: Both are important. Choose the dimension that fits the marketing goal you want to optimise or monitor.
-
-
Q: Besides Session source / medium and First user source / medium, what other UTM-related dimensions are there?
-
A: The UTM-related dimensions are:
-
Campaign name: the dimension that corresponds to the utm_campaign parameter. It identifies a specific campaign, such as a summer sale or a product launch.
-
Campaign term: the dimension that corresponds to the utm_term parameter. It is usually used to identify paid search keywords.
-
Campaign content: the dimension that corresponds to the utm_content parameter. It distinguishes different ads or links within the same campaign, such as ad version A and ad version B.
-
-
GA4’s Session source / medium and First user source / medium are easy to confuse, but both are important for understanding user behaviour. Used well, they help you evaluate campaign performance more effectively, understand the user journey and improve your marketing strategy, so your website traffic and conversion rates keep rising. If you have any questions or needs, get in touch.
