Real User Monitoring

Real User Monitoring (RUM) is a technique that measures your website’s performance with actual visitors, in their own browser, on their own device. Instead of simulated tests, RUM collects data on load times, interactions and errors whilst real users navigate your site. You can see exactly how quickly pages load for someone with a slow mobile connection in Groningen, or for a visitor using an outdated browser in Antwerp. For small and medium-sized companies, this is valuable because you’re not working with assumptions, but with hard figures on how your website actually performs in practice.

How Real User Monitoring works technically

RUM uses a small piece of JavaScript code that you embed in your website. This code sends performance data to a collection platform as soon as a page loads. Think of metrics such as Time to First Byte, Largest Contentful Paint and Cumulative Layout Shift – all Core Web Vitals that Google takes into account in its rankings. The script also records which browser, device and location the visitor is using. Unlike accessibility testing in a controlled environment, RUM measures performance in the real world of actual users. Platforms such as Google Analytics 4, Sentry or Cloudflare Web Analytics offer RUM functionality. The data starts flowing as soon as visitors access your site, allowing you to spot patterns emerging within an hour.

Why Real User Monitoring became – and remains – relevant

Synthetic monitoring, where you use a tool such as Lighthouse to simulate a test environment, has one major drawback: it does not reflect the diversity of your real audience. A visitor with a slow 3G connection on a train experiences your site very differently from your fibre-optic test environment. RUM emerged when companies realised that simulated tests were too optimistic. This is particularly crucial for online shops and platforms with a wide range of target audiences. In practice, we often see with SME clients that mobile loading times are twice as long as desktop times – something you can only pinpoint accurately with RUM. Now that Google uses page speed as a ranking factor, insight into real-world performance is no longer a luxury.

What Real User Monitoring delivers for your company

With RUM, you can see which pages load slowly, on which devices and for which target audiences. An online shop with 500 products might discover that product pages load 4 seconds slower on Android devices than on iOS, leading to a drop in conversions. You can set priorities: first optimise the slowest pages that receive the most traffic. Combined with a well-thought-out SEO strategy, you’ll not only improve rankings but also the user experience. RUM data also helps justify investments in faster hosting or front-end optimisation. You have hard figures rather than assumptions. For a B2B service provider with 12 employees, this could mean you finally understand why visitors drop off on the contact page: not because of the content, but because the page takes 6 seconds to become interactive.

Real User Monitoring is not an end in itself, but a means of identifying and resolving specific problems. Its applications range from conversion optimisation to technical troubleshooting. Below are four scenarios in which RUM makes a difference for Dutch SMEs.

Optimising the conversion funnel with genuine performance insights

An online shop notices that visitors are dropping out en masse at the checkout page, but doesn’t know why. RUM reveals that the page takes an average of 7 seconds to become interactive on mobile, whilst competitors are at 2 seconds. The problem turns out to be an overly heavy payment module that hasn’t been properly optimised. By addressing this bottleneck, the conversion rate increases by 18 per cent. In practice, we often see with SME clients that a single slow step in the funnel is responsible for 40 per cent of drop-offs. RUM makes this measurable and prioritisable. You can also segment your data: perhaps Android users perform worse than iOS users, or visitors from Belgium experience longer loading times because the server is located solely in the United Kingdom. This allows you to make targeted improvements rather than guessing.

Detect and resolve technical incidents quickly

A SaaS platform suddenly notices a spike in error messages and slow response times. RUM data shows that the problem only occurs for users of a specific version of Chrome on Windows 11, following a recent update. Without RUM, it would take weeks to identify the cause. With RUM, you can isolate the problem within an hour and roll out a workaround or patch. This is particularly valuable for companies with a diverse user base. Another example: following a deployment, the Cumulative Layout Shift suddenly increases. RUM points to a new advertising banner that is loading too late and causing the layout to shift. You can pause or adjust the banner before customers start complaining. Many companies combine RUM with backup strategies and monitoring to minimise downtime.

Improving SEO performance via Core Web Vitals

Google has been using Core Web Vitals as a ranking factor since 2021. Synthetic tools such as PageSpeed Insights provide an indication, but RUM shows how your site actually performs for visitors. A consultancy firm with 20 employees discovered via RUM that their blog pages had a poor Largest Contentful Paint score on mobile due to oversized header images. They optimised the images and saw a 25% increase in organic traffic within two months. RUM helps you prioritise: which pages have the most traffic and the worst scores? Tackle those first. Combined with technical SEO optimisation, you’ll build a solid foundation for better rankings. Important: RUM measures what real users experience, not what a controlled test predicts. This makes it more reliable for SEO decisions.

When Real User Monitoring is the right choice and when it isn’t

RUM is valuable if you have a website with substantial traffic – at least several hundred visitors per week. Below that, the dataset is too small to identify reliable patterns. It is also useful if you have a diverse audience in terms of device, location or browser, or if you regularly roll out updates and want to see quickly if anything goes wrong. RUM is less useful for static websites that rarely change and have low traffic. Also, if you haven’t yet carried out basic optimisations, such as compressing images or setting up caching, synthetic monitoring is a better first step. RUM really comes into its own when you want to move from assumptions to data-driven optimisation. For a start-up online shop with 50 visitors a day, Google Analytics 4 is sufficient; for an established player with 5,000 visitors a day, RUM is indispensable.