The short version: Google Analytics (GA4) tracks pageviews, clicks, scroll depth, session length, traffic source, device type, and rough location for anyone whose browser lets the tracking code run. It does not track every single visitor: ad blockers, cookie banner refusals, and browser privacy settings filter out a real chunk of your audience before it ever reaches your dashboard. Most business owners treat their GA4 numbers as the full picture when they are usually missing a fifth or more of what happened on their own site.
What Google Analytics tracks by default
When you install GA4 (that’s the only version now, Universal Analytics stopped collecting data back in July 2023), it starts tracking a handful of things the moment the tracking snippet loads in someone’s browser:
- Page views, including the URL, page title and referrer
- Scroll depth (it fires an event once someone scrolls 90% down a page)
- Outbound clicks (someone clicking a link that takes them off your site)
- Site search (if someone uses your on-site search box)
- Video engagement on embedded YouTube videos
- File downloads (PDFs, docs, common file types)
- Session start and session duration
These are called Enhanced Measurement events and most of them are switched on automatically when you set up a GA4 property. This is a big change from the old Universal Analytics, where you had to set most of this up by hand. It’s convenient, but it also means a lot of people believe GA4 is tracking things they never configured, and it makes the tool feel smarter than it is.
The event model: how GA4 sees your site now
Every single thing GA4 records is an “event.” A pageview is an event. A scroll is an event. A form submission, if you set it up, is an event. This is different from old-school analytics tools that separated “pageviews” from “goals” from “events” into different buckets. In GA4, it’s all one stream of events tagged with parameters.
This matters practically because it means the reports you see are only as good as the events you’ve defined. If you want to know how many people submitted your contact form, GA4 will not tell you that out of the box. You have to mark that specific button click or page load as a conversion event yourself, inside the GA4 admin panel, under Events, by toggling “mark as conversion” next to the event name. Skip that step and you can have thousands of visitors and zero visibility into who asked for a quote.
Location, devices and audience data
GA4 also builds a rough profile of who’s visiting, based on:
- IP address, which it uses to estimate city and country, then discards (Google does not store your visitors’ full IP addresses long term)
- Device type, browser, and operating system
- Screen resolution
- Language settings
- If you’ve turned on Google Signals, some demographic and interest data pulled from people who are signed into a Google account and have ad personalisation switched on
That last point is worth sitting with for a second. Google Signals only works for the slice of your visitors who are logged into Google and haven’t opted out of ad personalisation. For most B2B sites I audit, that’s a minority of traffic, so the age and gender breakdowns you see in GA4 are built from a sample, not your whole audience. Treat them as a rough steer, not a fact.
What it doesn’t track (and why your numbers are lower than reality)
Here’s the bit most explainer articles gloss over: your GA4 dashboard was never a full count of every person who visited your site, and pretending otherwise leads to worse decisions, not better ones.
Three things quietly reduce your recorded numbers:
- Ad blockers. uBlock Origin, Brave’s built-in blocker, and privacy extensions block the GA4 script from loading at all. Estimates of ad blocker use in the UK sit around 25 to 30% of desktop browsers, higher among tech-literate and B2B audiences.
- Cookie consent refusals. If your site uses a proper consent banner and someone clicks “reject,” most GA4 setups stop tracking that visit entirely (unless you’ve built consent mode with modelling, which most small sites haven’t).
- Browser privacy defaults. Safari’s Intelligent Tracking Prevention and Firefox’s Enhanced Tracking Protection restrict or shorten how long tracking cookies survive, which fragments sessions and undercounts returning visitors.
Stack those together and it’s entirely normal for GA4 to be undercounting real visits by 15 to 40%, depending on your audience. Nobody wants to say that in a “how does Google Analytics work” post because it makes the tool look less trustworthy, but it’s the truth, and it changes how you should read your reports. Treat GA4 numbers as directional, not exact, and always sense-check them against a second source.
A real example from a client audit
I sat down with a client last year, a B2B services firm, to work out why their sales team said enquiries were up but GA4 showed sessions flatlining. We pulled their hosting provider’s raw server logs for the same month and compared them to GA4. Server logs showed roughly 19,000 requests to key pages. GA4 recorded just under 13,000 sessions for the same period, a gap of about 32%.
We dug into why. Their site had a cookie banner from a compliance plugin that defaulted to “reject” unless someone actively clicked accept, and most people simply closed the banner without engaging. On top of that, a decent share of their traffic came from LinkedIn’s in-app browser, which handles tracking scripts inconsistently. Once we fixed the consent banner to make “accept” the more natural first click (still fully compliant, just better designed) and set up server-side tagging for their key form, recorded sessions rose by roughly 22% the following month with zero change in actual traffic. The visitors were always there. GA4 just hadn’t been seeing most of them.
That’s the story I tell every client now who’s convinced their marketing has stopped working when their tracking has. Before you panic about a traffic drop, check whether it’s a tracking problem before you assume it’s a demand problem.
How to check exactly what’s firing on your own site
You don’t need to guess. Here’s how to see, in real time, exactly what GA4 is recording on your site:
- Open your GA4 property and click Reports, then Realtime. Browse your own site in another tab and watch your visit show up within seconds.
- Install the Google Tag Assistant Chrome extension, connect it to your domain, and it will show you every tag firing on each page, including GA4, and flag ones that are broken or missing.
- Turn on DebugView in GA4 (Admin > DebugView) alongside the Tag Assistant to see every single event and parameter being sent, live, as you click around.
- Cross-check your numbers monthly against Google Search Console, which measures impressions and clicks from search independently of GA4’s cookie-based tracking, so it’s a useful sanity check when the two tools disagree.
- If you run ecommerce or lead forms, check your CRM or payment processor’s own count of orders or leads against what GA4 reports as conversions for the same date range.
This whole process takes about twenty minutes and it’s the single most useful thing you can do before making any decision based on your analytics.
The tracking most small businesses forget to switch on
Enhanced Measurement gets you the basics, but the events that tell you whether your marketing is working usually need setting up by hand:
- Form submissions (successful ones, not just page loads of your contact page)
- Phone number clicks on mobile, using GA4’s built-in “click” event with a URL parameter filter
- WhatsApp or Calendly link clicks
- Newsletter signups
- Add-to-cart and checkout steps for ecommerce sites, using GA4’s ecommerce event set
If none of these are marked as conversions, GA4 will happily tell you that your blog post got 4,000 views while giving you no idea whether any of those readers ever became a lead. This is exactly the gap that a decent lead generation strategy depends on closing, because traffic without conversion tracking is just a vanity number dressed up as insight.
Cookie consent and what that does to your data
Under UK GDPR and the EU equivalent, you’re required to get consent before running non-essential tracking cookies, and GA4 counts as non-essential. This means every visitor who declines consent is a visitor GA4 will not see at all, unless you’ve set up Google’s consent mode, which uses modelling to estimate the missing behaviour rather than measuring it directly. Most small business sites I look at have never touched consent mode, which means their real traffic is always somewhat higher than their reports show, and always will be, by design, not by accident.
It’s worth saying plainly: platforms limit what you’re allowed to see about your own audience everywhere, not just here. If you’ve ever tried to work out who doesn’t follow you back on Instagram, you’ll know the platform doesn’t hand that data over easily either, and you end up needing workarounds just to see basic facts about your own following. Analytics tools, social platforms, ad platforms, they all sit between you and your own audience data more than most business owners realise.
What to do with all this
Don’t rip out GA4 over any of this, it’s still free and it’s still the most widely used tool for a reason. But stop treating the number on the homepage of your dashboard as gospel. Set up your conversion events, cross-check against Search Console and your own CRM monthly, and build a habit of asking “is this a tracking gap or a real drop” before you change strategy based on a dip. If you want a wider view that pulls in more than just GA4, our guide to effective web analytics walks through the other tools worth layering on top, and the Finteza-based approach to analytics is worth a look if you want cookie-free tracking that doesn’t drop as much data to consent refusals. And if you’re juggling GA4 alongside your CRM, ad accounts and social numbers, it’s worth reading about how to pull your whole business into one dashboard so you’re not logging into six tabs every Monday morning trying to work out if last week went well.
It also helps to spy on a competitor’s website traffic without paying for an expensive tool.
Frequently asked questions
Does Google Analytics track individual people by name?
No. GA4 does not collect names, email addresses or other directly identifying information unless you manually send that data yourself, which Google’s terms forbid you from doing. It tracks anonymised client IDs tied to a browser or device, not a named person.
Why does Google Analytics show fewer visitors than I expect?
Ad blockers, cookie consent refusals, and browser privacy settings like Safari’s Intelligent Tracking Prevention all stop GA4 from recording a visit, which typically undercounts real traffic by 15 to 40%. Cross-check against Google Search Console or your server logs if the numbers feel off.
Does Google Analytics track how long someone stays on a page?
It tracks “engaged sessions” and average engagement time, which measures active time spent with your site in focus, not simply how long a tab stayed open in the background. It replaced the old “average session duration” and “bounce rate” metrics from Universal Analytics.
