Blog

At RUMvision, our focus is helping site owners make their sites faster. To do that well, we depend on the data browsers give us through APIs. Some of those APIs are already incredibly useful — but not all browsers support them consistently.

For years, site owners have been using Subresource Integrity (SRI) as a way to ensure that third-party scripts can’t be tampered with. However, keeping your script up to date is one of its challenges.

If you’ve been tracking real user performance, you probably already know: Chrome has long supported largest contentful paint (LCP), but Safari until now did not. That’s starting to change, and it’s a big deal if you rely on rumvision for insights.

Moin Kiel! I was happy to get everyone up to speed debugging and optimizing Core Web Vitals with RUM + DevTools. Looking for the slides? Here you go!

On July 18th I got to talk about about webperformance, while shipping and sipping at Mollie's biggest developer meetup yet! Here you find the slides.

Many agencies struggle with performance conversations because they rely on synthetic testing alone. Here's how Real User Monitoring changes the game and what we've learned communicating these insights to clients.

On June 10th 2025 I gave my talk "Why your pagespeed score is lying to you". In this you'll find the slidedeck, more info on how to improve the webperformance of your Magento shop and even info on a special we're running!

"Your site is slow" – four words no Hyvä developer wants to hear, yet only 51% of Hyvä shops achieve good Core Web Vitals scores. After years of optimizing Magento performance, we've identified the common issues preventing stores from reaching their full potential. In this guide, we'll explain not just what to fix, but why things fail in the first place. Your journey to better Core Web Vitals – and happier customers – starts here.

What happens to ecommerce when the lights go out? On April 28, 2025, a massive power outage hit Spain and Portugal just before noon. We combined electricity demand data with our own data, how others experienced it and the impact of an outage on ecommerce and non-ecommerce.

You want to ship native lazyloading or popovers to get rid of JavaScript and improve INP. And rather sooner than later. But there's a challenge: how to know if all of your users are ready for that feature?Baseline, a browser-wide initiative tracking 1000+ web features, is changing this. And with RUMvision's Baseline integration, you know exactly when your real visitors are ready for shipping modern features.

At RUMvision, we're always looking for smarter ways to optimize web performance data collection. That's why we're excited to announce we've begun rolling out support for a new browser API called fetchLater.

If you're still depending on unload events in your code, you need to act NOW. Chrome is starting to kill these handlers this month, potentially breaking your website's analytics and data-saving features. These events were never reliable on mobile, Safari already ignores them, and soon desktop Chrome will too. Here's why moving to better alternatives won't just save your code—it'll actually improve your site's performance.

Chrome is about to supercharge page navigation for millions of websites by ignoring a common performance-killing HTTP header. This under-the-radar change could dramatically improve your Core Web Vitals with zero developer effort by enabling bfcache for pages with Cache-Control: no-store. How do you know if you will benefit? (Spoiler: if you're using Magento, you probably won't.)

The back/forward cache (bfcache) is the most powerful performance optimization you've never heard of. While teams obsess over milliseconds of server time, they're missing out on entire seconds of improvement that's already built into every major browser.

January 26th, 2024 marks one year since all major browsers fully supported AVIF. For years, developers used `picture` elements to provide WebP or AVIF images while falling back to JPEG for browsers lacking support. Now, with universal AVIF compatibility, these workarounds may no longer be necessary.

Keeping up with web technologies can be overwhelming, especially for product owners who aren’t deeply technical or developers who want to avoid the complexity of polyfills. Baseline is an initiative that helps developers and businesses understand which web features are safe to use across all major browsers.

We're excited to announce the implementation of View Transitions API on our website, enhancing navigation fluidity and user feedback. This helps both us and you as a visitor to smoothly navigate our website from the very start of 2025. This UX update not only makes navigation more visually appealing, it also provides better feedback about page load states.

In 2024 we weren't only the sponsor but were also speaking at a sold out Performance.now() conference.

Core Web Vitals and SEO – it's a hotly debated topic that often leaves business owners and SEO professionals wondering where to focus their efforts. Some claim it's the key to ranking success, while others argue it's just another optimization rabbit hole. Let's cut through the noise and focus on what actually matters for your business in 2024 and beyond

The srsltid auto-tracking parameter already caused SEO havoc amongst site owners using Google Merchant Center. But issues aren't stopping there.