One of the most popular reports within the Universal Analytics version is definitely the Source/Medium Report.
In this Report, you can quickly observe the source and medium of users landing on the website.
In UA we can find it under Acquisition > All Traffic > Source/Medium

The new version of GA4 offers many features but there is still no Report with this dimension.
In fact, if we try to explore the Acquisition report we find several entries but not the one with source/medium.
In this post I want to show you how the new Google Analytics 4 behaves and what dimensions we have available.
Acquisition Report in GA4
A number of Reports are available in Google Analytics 4 that offer a more qualitative User Interface than the Universal Analytics version.
Within the Acquisition Report it is possible to find a series of reports:
- Acquisition overview: shows an overview of the channels from which users land on the website;;
- User acquisition: shows which is the first channel of a user who landed on your website;
- Traffic acquisition: shows which are the channels of the different sessions that have browsed the site;

Each of these Reports offers a set of primary and secondary dimensions that can be added to analyze user behavior, as you see in the image below:

However, exploring the primary dimension of Acquisition reports, we do not find the ‘source/medium‘ dimension that was in Universal Analytics:

Despite this, thanks to the enormous flexibility offered by the GA4 UI, we can create by ourselves the Report with the dimension of our interest and update the list of available Reports.
However, we need to pay attention to the name of the new dimensions in GA4 and get some clarity on where they apply, before creating our Report.
Also, remember that GA4 is different from UA: as also written in the Official Guide, each session is associated with only one Source or Campaign and does not start a new session if GA4 encounters a new Source or Campaign.
Source and Medium Dimensions in GA4
Scrolling through Google’s official guide we find several dimensions that refer to the Source and Medium of the users’.
In addition, we also find different Scopes for the Traffic’s dimensions.
Let’s try to make a summary list to clarify:
Dimension | Available in | Scope | Parameter | CoreReporting API |
Source/Medium | Attribution | Event | utm_source, utm_medium | sourceMedium |
First user source/medium | User Acquisition | User | utm_source, utm_medium | firstUserSourceMedium |
Session source/medium | Traffic Acquisition | Session | utm_source, utm_medium | sessionSourceMedium |
As we can observe, the ‘source/medium‘ dimension seems to be different in GA4 than in UA.
It is available for the Attribution Report and is event-scoped so it is a dimension that is about what brings the user to a new session within which a Conversion occurs.
Also, Google tells us that event-scoped dimensions have the feature of having only the “dimension name” within them, such as “Source“.
Let’s make a test, comparing the ‘source/medium‘ dimension with the ‘Session source’ and ‘Session medium‘ dimensions.
In the next steps I’ll explain how to try to create the ‘Source/Medium’ Report and then we’ll see the differences between the traffic dimensions.
Create Source/Medium Report in GA4
To create our Custom Report and save it to always have it available, just follow these simple steps.
Step 1 – Acquisition Report
Go to one of the Acquisition Reports in Google Analytics 4.
In my example, I will go to the Traffic acquisition report:

Step 2 – Click on ‘Customize Report’
Now click on the top right of the pen icon where it says ‘Customize Reports‘.

Click on the icon to edit the report you are viewing.
Step 3 – Select the dimensions to modify
Now that we are inside the customization of the Report, let’s select ‘Dimensions‘ in order to modify the dimensions that interest us:

Then we click on ‘+ Add dimension‘ and choose the ‘source/medium‘ dimension.

We look for the ‘source/medium‘ dimension:

Step 4 – Remove the dimension that do not interest us
Now we need to clean up the report, removing the dimensions we don’t care about and leaving only the ‘source/medium‘ dimension.
Just click on the three dots and click on the command ‘Remove‘.

Once we have removed all dimensions, we can click ‘Apply‘ to save the report:

Step 5 – Save the source/medium Report in GA4
Once we have changed the dimensions, we can save the Report by clicking on the ‘Save‘ tab.
We see that the new Report will already have the name with the newly inserted dimension i.e. ‘Traffic acquisition: Source/Medium‘.

There will be two options that you can choose based on your needs:
- save changes to current report: modifies the current Traffic acquisition report, replacing it with the Source/Medium dimension only
- sava as a new report: creates a new specific Report with the source/medium dimension only
In my example I will select ‘save as a new report‘ to add the report among the others already present:

Step 6 – Rename the Report
If you save the new report as ‘new report‘ you will need to give it a name so that you can easily find it in the Google Analytics 4 UI list.

Step 7 – Go to GA4 Library
Once the report is saved, you will need to go to the Library to make the Report available.
To access the Library simply click on ‘Library‘ under all Reports:

Now, select ‘Life cycle‘ to be able to edit its structure:

Look for the report you just created, the one I called ‘Traffic acquisition: Source/Medium‘ in my example, and drag it from the right to the left block in the ‘Acquisition‘ Report:

And save it.
Once you have saved, the Report will be available in the Google Analytics 4 User Interface:

Edit Report in GA4
If you find that you want to make changes to the name of the report you just created, remember that you can do so at any time.
Go to the ‘Library‘ part and click on the Report you just created to, for example, rename it: click on the three dots and select ‘rename‘:

You can edit the name and save.

Within Library you can also change the dimensions and metrics of the report you just created or move it to another position.
Differences between ‘Source/Medium’, ‘Session source’ and ‘Session medium’
Now that we’ve created the Custom Report with the ‘source/medium‘ dimension, let’s try to see the difference in values that are collected compared to the other dimensions.
To view the Report with the ‘Session source‘ and ‘Session medium‘ dimensions, simply:
- Go to the Traffic acquisition
- Select ‘Session source‘ as a primary dimension
- Secelct ‘Session medium‘ as a secondary dimension

If we compare the Report’s data with the ‘source/medium‘ dimension vs. the Report with the two dimensions above, the difference is as follows (values taken as an example from a GA4 Property):
Report | Metric: Users | Δ% | Metric: Sessions | Δ% |
Report ‘Session source’ and ‘Session medium’ | 625,366 | 835,790 | ||
Report ‘source/medium’ | 93,491 | -568,9% | 409,549 | -50,99% |
The difference is clear and the reason is the Scope on which the chosen dimension is based.
Conclusions
In this post, we started from the ‘source/medium‘ dimension in a dedicated Universal Analytics Report and tried to look for the same dimension in Google Analytics 4.
What we have observed is that the name of the dimension is the same between the two versions of GA, however the purpose, underlying the dimension, is different.
We can conclude that the closest dimension to ‘source/medium‘ in Universal Analytics is the ‘Session source/medium‘ dimension in GA4.
However, the ‘Session source/medium‘ dimension is only available in the Explore section of GA4:

Alternatively, I can use the combination of primary and secondary dimension within the Traffic Acquisition Report:

I hope that soon Google will also make the ‘Session source/medium‘ dimension available as a primary dimension in the Traffic Acquisition Report, not forcing us to create a Report in Explore to have this primary dimension available.
GA4 is constantly being updated, so I wouldn’t be surprised if, shortly, this will happen
Good analysis!
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