Google Analytics 4, GA4 for short, is Google's website and app measurement tool. It records where a visitor came from, which pages they saw, what they added to the basket and whether they bought. In 2023 it replaced the previous version, Universal Analytics, and changed the logic of measurement: it no longer counts "page views" but "events"; opening a page, pressing a button, viewing a product and buying are all records of the same kind. The tool is free, and it is installed with a snippet of code or through Google Tag Manager.
What Is GA4 For?
Ad panels show you the click and the conversion they count themselves; they do not show what the person did after reaching the site. GA4 fills that gap. Of the 1,000 people who arrived from Google Ads, how many reached a product page, how many added to the basket, how many gave up at the payment step, how many came back three days later through organic search and bought; all of that lives in GA4. It is also the only place that puts ad, organic search, social media and email traffic side by side with the same yardstick.
It does three things well: comparing channels, following on-site behaviour step by step and deciding by its own rules which source an e-commerce sale belongs to. It does not do two things: it does not know ad spend, so on its own it cannot give you ROAS, and it does not hold the customer's identity; it tells users apart by cookie, and when the same person arrives from two devices it usually counts two users.
What Changed From Universal Analytics?
For those who used the old version, the biggest difference is the unit of measurement. Universal Analytics counted sessions and page views; GA4 records everything as an event, and sessions are derived from those events. That is why the numbers of the two versions never match exactly, and expecting them to is wasted effort. The second difference is that "conversions" were renamed "key events"; the events you mark, such as purchases, form submissions and phone clicks, are reported under that name. The third is that bounce rate was replaced by "engagement rate": a session lasting more than 10 seconds, viewing two pages or producing a key event counts as engaged.
Universal Analytics
Session and page view oriented. Bounce rate. Goals. Last-click attribution by default. Data kept indefinitely.
GA4
Event oriented; a page view is an event too. Engagement rate. Key events. Data-driven attribution by default. In standard accounts event data is kept for 2 or 14 months.
Retention is a setting that gets overlooked: the default is 2 months, after which you cannot reach older data in detailed exploration reports. Raising it to 14 months in property settings is one of the first things to do; the menu path changes between versions, so searching for "data retention" is enough.
Setup: Property, Data Stream and Tag
In GA4 an account holds properties, and a property holds data streams. When you open a web data stream for your site you receive a measurement ID starting with "G-". You put that ID on the site in one of two ways: by adding the Google tag code directly to every page, or through Google Tag Manager. The second way means you will not need a developer later when adding ad conversion tags and the Meta pixel; even for a brand-new site, setting up through Tag Manager is less work. Platforms such as ikas, Shopify and T-Soft offer a ready field where you enter the measurement ID; most of them send the e-commerce events themselves as well.
After setup, seeing your own visit in the real-time report is the fastest way to confirm the tag works. Then make two settings straight away: link the Google Ads account and extend data retention. Google's own setup guide is explained step by step in the Analytics help centre.
Key Events and E-commerce Events
GA4 collects some events on its own: page views, scrolling, outbound link clicks, file downloads, site search. E-commerce events have to be sent by the site, and Google has set standard names for them: product view (view_item), add to basket (add_to_cart), start of checkout (begin_checkout) and purchase (purchase). When those names and the parameters the event carries, such as product, price and currency, are followed, GA4's monetisation reports fill themselves. If your platform sends these events, most of the work is done; if not, this is where Tag Manager setup is needed.
When you mark the purchase event as a key event, GA4 starts distributing it by channel and campaign. On lead-generation sites, form submissions and phone clicks take the same role. The most common mistake here is treating a page view as a key event: seeing the "thank you" page is not a purchase, and it counts twice when the page is refreshed.
Reports to Check Regularly
Sessions by channel: organic search, paid search, social, email, direct. Here you see which channel brings traffic and each channel's engagement rate.
Most viewed pages, average time on page, number of key events per page. Shows which product page sells and which blog post is read and abandoned.
Views, add-to-basket and purchases by product. Products viewed but not added to the basket point to a price or image problem; products added but not bought point to the shipping and payment step.
When the standard reports are not enough, the Explore section offers free-form tables, funnels and path analysis. Building the checkout funnel step by step is the only way to surface a finding like "40% of users are lost on the payment page"; it is invisible in the standard reports.
Attribution: Which Channel Gets the Sale?
A user first arrives through an Instagram ad, then two days later searches your brand name on Google and buys. Who does this sale belong to? By default GA4 uses data-driven attribution: it shares the sale among the touchpoints according to its own model. Google Ads credits the same sale entirely to itself, and so does Meta. That is why you see three different numbers in three panels; in why Google Ads and GA4 conversions differ we explained which one to trust in which situation. The practical rule: use the ad panel to compare campaigns, use GA4 to compare channels.
Linking Google Ads and Search Console
When Google Ads is linked, GA4 matches ad clicks with campaign names and you can target GA4 audiences in Google Ads; Google Ads can also import GA4 key events as conversions. The Search Console link brings organic queries into GA4's acquisition report. Both are done in a few clicks from the product links section in admin settings and do not work retroactively; every day you postpone linking is lost data.
GA4's limit is that it does not see ad spend or the data on the Meta side. AdsLuma combines GA4 with Google Ads, Meta, Search Console and store data on the same screen; the sale in GA4 and the conversion in the ad panel sit side by side, and you can ask Luma AI where the gap opens.
Frequently Asked Questions About GA4
Is GA4 free?
Yes. The standard version is free and more than enough for most sites. The paid version, Analytics 360, is for very high-traffic sites and enterprise data needs.
What is the difference between GA4 and Universal Analytics?
GA4 measures by event; Universal Analytics was based on sessions and page views. Conversions became "key events" in GA4, engagement rate replaced bounce rate, and the default attribution model became data-driven. Universal Analytics stopped processing data in 2023.
Do I need a developer to set up GA4?
On most e-commerce platforms, entering the measurement ID in a settings field is enough. On custom sites, setup through Google Tag Manager needs technical knowledge but not code writing; getting developer support once so that e-commerce events are sent with the right parameters makes the job easier.
Why does GA4 show a different conversion count from Google Ads?
The two tools assign a sale to a channel by different rules: Google Ads by the last ad click, GA4 by its data-driven model. Conversion windows, cookie consent and device switching widen the difference. The gap is not an error; the two tools should be used for different questions.
AdsLuma combines the behaviour GA4 sees with ad spend and real order data; ask Luma AI which channel is actually selling.
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