You will be able to explain the main GA4 metrics and the limits of each.
Farah's partner looked at the GA4 overview and asked why the shop had 3,100 users last month when they had sold to only about 200 people and had maybe 2,000 on the mailing list. Did 3,100 different people really visit? Farah did not know. She had been reporting the number for months without being sure what it counted.
Every GA4 metric has a definition and a blind spot. You do not need to memorise the help centre, but you do need to know what the few numbers you report actually measure, so you can explain them to someone else and know when not to trust them.
When GA4 counts a user, it is usually counting a browser on a device that it has given an identifier to. The first time someone visits, GA4 stores an identifier in a cookie in their browser. Later visits from the same browser carry the same identifier, so they count as the same user.
That works until real life gets involved. A customer who browses Farah's shop on her phone during the MRT ride and buys on her laptop at home is two users. The same customer using a different browser on the same phone is two users. Someone who clears cookies becomes a new user. A family sharing one tablet is one user.
So the user count is an estimate of people, and usually an overestimate. GA4 can join devices more accurately if you send your own user ID when people log in, or through signals from Google accounts, but most small sites do not have that set up, and even then the match is partial.
For Farah's partner, the honest answer was: about 3,100 browsers visited, which means fewer than 3,100 people, and we cannot say exactly how many fewer. The number is still useful for comparing one month with another, as long as the way it is counted does not change.
A session is a visit: a period of activity from one user that starts when they arrive and ends after a stretch of inactivity. One user can have several sessions in a month, which is why sessions are usually higher than users.
Not every session means much. Someone who taps an Instagram link, sees the page start to load and swipes back has created a session. GA4 separates these by counting engaged sessions. By Google's definition, a session is engaged if it lasted longer than a set time, or included a key event, or had two or more page views. Google's GA4 help centre gives the default time as 10 seconds, and you can change it in the data stream settings, though most businesses leave it.
Engaged sessions are the better number to watch when you compare channels. A campaign that brings 1,000 sessions of people who leave at once is worth less than one that brings 400 sessions of people who look around.
Engagement rate is engaged sessions divided by all sessions. If Farah's shop had 2,000 sessions last month and 1,240 were engaged, the engagement rate is 1,240 divided by 2,000, or 62 percent. Those are example figures, but the sum is the one GA4 does.
GA4 made engagement rate the main measure of visit quality. Older Google Analytics led with bounce rate, the share of visits that saw only one page. That penalised pages where people found what they needed and left, such as a contact page or a blog post that answered the question. GA4 does still show a bounce rate, but it is now simply the share of sessions that were not engaged, so it is the opposite of engagement rate. If you compare a GA4 bounce rate with one from an old report, you are comparing two different measures with the same name.
Engagement rate is most useful in comparison: one channel against another, one landing page against another, this month against last. There is no universal good number. A product page and a blog post will never have the same rate, and nor will two different businesses.
There is one more gap to know about. Visitors who decline analytics cookies on your banner may not be recorded at all, or only partly. If you use Google's consent mode, GA4 may fill some of the gap with modelled data, which is an estimate based on the visitors who did accept. Ad blockers and some browser privacy settings also stop the tag from loading.
The share of missing visitors differs by site, audience and banner design, so there is no correction factor to apply. What it means in practice is that GA4's totals are estimates, and your shop, booking system or CRM is the place to count real sales and enquiries. Lesson 5.2 comes back to this when the numbers from different tools disagree.
When Farah explains the numbers to her partner now, she leads with orders from the shop platform, then uses GA4 to explain where the buyers came from and how the visits behaved. Writing that kind of plain explanation for someone who has never opened GA4 is a good test of whether you understand the metrics yourself, and it is what you will do next.
Write a one-paragraph explanation of users, sessions and engagement rate for a colleague or client who has never opened GA4.
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