Two cookie banners could be wrecking your analytics

Ella Pybus | 1 October, 2026 | 8 minute read | Blog, Tracking and Analytics

If your bounce rate suddenly jumped around the same time you added a cookie consent banner, it’s easy to assume the banner itself is the problem. But quite often, the real issue is something much less obvious: there are actually two consent banners running on the site at the same time.

We see this more often than you’d think when we’re looking through analytics and attribution setups. A business will have one consent management platform in place and working properly, but somewhere in the background there’s another one still active.

It might have been left behind after a website migration, added through a plugin, bundled into a CMS, or pushed through Google Tag Manager by someone who didn’t realise there was already a consent tool in place.

On the surface, the site might look completely normal. You may only notice one banner, or the second one might flash up so quickly that nobody spots it. But behind the scenes, both tools can still be trying to control the same consent signals, and that’s where the problems start.

Why two cookie banners can mess with your data

A cookie banner isn’t just there to annoy people with an “accept” button. It plays an important part in telling your analytics and advertising platforms whether they’re allowed to collect and store data.

In a Google Analytics setup, that usually means sending consent signals that tell GA4 and other Google tags whether tracking is allowed. When you have one consent platform doing that job, everything is relatively straightforward. But when two tools are both trying to control the same signal, they can start contradicting each other.

One banner might tell Google that consent has been granted, while the other is still telling it that consent has been denied. Whichever one updates the consent state last can effectively win, and because scripts don’t always load in exactly the same order on every visit, the result can change from one user to the next.

That means one session might be tracked properly, another might only be partially measured, and another could end up firing duplicate tracking altogether. Once that happens, your analytics stop behaving consistently, and that’s when it becomes difficult to trust what you’re seeing.

To put this into context: studies suggest that even a single, correctly configured consent banner can cost you a large share of your measurable traffic, etracker’s benchmark research found an average of around 60% of visit data is lost when consent is required. When two banners are fighting over the same signal, that loss becomes unpredictable on top of being large, which is exactly what makes the data so hard to trust.

What that looks like in GA4

One of the most common issues is blocked or delayed measurement. If one of the consent tools keeps GA4 in a denied state for the first few seconds of the visit, the opening part of the session may not be recorded properly. The visitor is still on your site and engaging with the page, but GA4 simply isn’t seeing all of it.

You can also end up with the opposite problem, where too much data gets recorded. If both consent tools release their own version of a GA4 tag, one page load can result in two pageview events. Suddenly pageviews are inflated, sessions don’t look right, and every metric built on top of those numbers becomes less reliable.

There’s also the user experience side of it. If two banners or overlays are sitting on top of each other, your visitor’s first few interactions may be spent dismissing consent messages instead of interacting with the actual website. Those clicks may never reach the page in the way you expect, which can further distort your engagement data.

Why bounce rate is often the first thing people notice

Bounce rate is usually the metric that makes people realise something has gone wrong, because the change can look quite dramatic.

In GA4, bounce rate is essentially the opposite of engagement rate. A session is considered engaged if the visitor stays for more than 10 seconds, completes a conversion, or views at least two pages.

Now imagine someone lands on your website, spends a few seconds dealing with two cookie banners, then reads the page for a while before leaving. From the visitor’s point of view, they may have genuinely engaged with the content. They didn’t land and immediately disappeared.

But if GA4 was blocked or delayed during those first few seconds, it may not have seen enough of the session to classify it as engaged. As far as the reporting is concerned, that visit can end up looking like a bounce.

When that starts happening across hundreds or thousands of visitors, your bounce rate can suddenly climb even though the actual behaviour of your audience hasn’t changed very much at all.

That’s the important distinction. The banner might not be making more people leave your site. It might simply be stopping you from measuring the people who stayed.

How to check whether this is happening on your site

The good news is that you don’t need to be a developer to spot some of the obvious warning signs.

Start by opening your website in an incognito or private browsing window. Watch what happens when the page first loads and pay close attention to the consent banner. If you see two banners appear, one stack on top of another, or a second message appear after you’ve already accepted the first one, that’s a strong sign that more than one consent tool is running.

You can also open your browser’s developer tools and look at the Network tab while the page reloads. If you filter for collect, you can see the requests being sent to Google Analytics. If you’re seeing duplicate GA4 requests on a single page load, it’s worth investigating whether more than one tracking setup is firing.

Another useful check is to search the page source for common consent management platforms such as Cookiebot, OneTrust, and CookieYes. It’s also worth checking whether your CMS, CRM or any of your plugins have their own consent tools enabled, because these are often the hidden source of the duplication.

For a more detailed check, Google Tag Manager Preview mode and GA4 DebugView can show you exactly how many times a page_view event is firing and what consent state GA4 is seeing when each event is sent.

How to fix it

Once you know there are multiple consent tools running, the fix is usually more about housekeeping than anything especially complicated.

The first step is to choose one consent management platform and remove the others properly. Simply hiding a second banner with CSS isn’t enough. If its scripts are still loading behind the scenes, it can continue to send consent signals and interfere with your tracking even though nobody can see it.

You also need to make sure only one tool is responsible for controlling consent mode. There should be one clear source of truth telling Google whether tracking is granted or denied. Everything else should work through that setup rather than trying to make its own decisions.

While you’re there, it’s worth checking Google Tag Manager for duplicate GA4 tags as well. This is incredibly common on older websites where several developers, agencies or internal teams have all made changes over time. What looks like one simple analytics setup can easily turn into two or three overlapping versions without anyone noticing.

Once everything has been cleaned up, treat the fix date as a fresh starting point for your reporting. If the previous data was affected by inconsistent consent signals or duplicate tracking, comparing it directly with the clean data that comes afterwards can be misleading. Make a note of when the issue was resolved and measure forward from there.

The bigger picture

A duplicate cookie banner sounds like a fairly minor technical issue, but the impact on reporting can be surprisingly large. It can be one of the reasons GA4 says one thing, your CRM says another, and neither seems to match the number of leads or sales you know the business is actually generating.

That’s why this is one of the things worth checking whenever your analytics suddenly stop making sense, especially if the change happened around the same time as a consent update, website migration or tag management change.

Before assuming your audience has suddenly changed, or deciding that a campaign, landing page or piece of content is underperforming, it’s worth checking whether the tracking itself is telling you the truth.

Not sure whether your data is telling you the truth?

If your GA4 numbers have stopped making sense and you can’t work out why, it’s worth having someone check them before you rewrite your strategy. Our team can audit your consent setup, tracking and reporting to find out what’s really going on. 

Book a discovery call and let’s get your data working properly again.