It’s the simplest question you can ask about a website, and most performance tools can’t answer it directly.

Lighthouse tells you if a page, tested in a lab, is well-built. APM tells you your servers are healthy. CrUX monitoring shows Google SEO ranking liabilities. All useful signals.

But, sometimes, you need to take a step back and ask:

How many of my users are having a good time on our site right now?

This question matters to your business. Visitors who have a bad time bounce, abandon their carts, churn, and forget all about you. When people have a good time, they convert at a much higher rate, and become return customers.

UX Rating answers that question.

What UX Rating measures#

UX Rating takes every real user session, evaluates key performance metrics, and identifies Good, Needs Improvement, or Poor user experiences into three buckets.

Calibre allows you to see what percentage of users had a Good time, and who suffered a frustrating or lacklustre experience with your brand.

UX Rating on the RUM Audience page, showing a stacked bar chart of good, needs improvement, and poor experience percentages over time.

UX Rating on the RUM Audience page in Calibre.

Lots of performance tools have a UX Rating like metric, but UX Rating in Calibre is the gold standard. Two things set it apart.

  1. Calibre RUM samples by user sessions, not just pageviews. It grades the experience of an actual person moving through your site.
  2. User experiences that feel slow or unstable are captured and recorded towards your UX Rating. Using Core Web Vitals and Time to First Byte (TTFB).

Delays felt by users are reflected and graded, meaning UX Rating provides a faithful assessment of user experience.

You can use UX Rating as a high-level health check, approximation of passing Core Web Vitals, and a way of locating problematic areas of your site.

Once you know you have a problem, you can use other specialised metrics to understand what is happening, and identify in-page elements that are hurting you most.

Why Good% is the number to watch#

Knowing what share of your users have an 'all good' experience is a powerful insight.

"Only 30% of customers are having a good experience" prompts action in a way that a LCP metric value or Lighthouse score doesn’t and can’t.

You can directly see the share of visitors leaving happy versus the share leaving frustrated. That directness brings focus. Focus moves the number.

Where UX Rating immediately paid off for Calibre#

A few weeks ago, our own UX Rating took a sharp dive. This isn’t a bit, it really happened.

Following changes to the website, we noticed that "Good" user sessions dropped from 85% to just 34%.

From our Audience report, we could immediately see what had happened. An update to our free Core Web Vitals checker tool had missed an important cache header. Every request was flowing straight-through our CDN, smashing the origin server.

Because the pages draw a lot of traffic, overall performance dipped as the server was busy processing requests. One missed header created a site-wide liability.

Audience report: UX Rating for Page Groupings. See UX Rating by Site section.

Audience report: UX Rating for Page Groupings. See UX Rating by Site section.

The Audience report automatically segments by Page Grouping, which pointed straight at a cluster of high-traffic dynamic pages: /tools/core-web-vitals-test/*.

We found and fixed the missing cache header. UX Ratings improved rapidly. A simple mistake does not have to be a big deal, and in this case, it wasn’t.

Since then, we’ve also used UX Rating to pinpoint other substandard areas of our site and improve them. All based on actual human experience.

Successful high-level metrics point the flashlight, and that’s exactly what UX Rating does.

UX Ratings create alignment and cut-through jargon#

UX Rating provides clarity that can bring everyone together with a shared understanding. There’s something for everyone:

  • Designers can uncover bumpy or frustrating user experiences to inform future design choices and implementation details that need polish.
  • Developers get a single signal that catches regressions and segments cleanly by page grouping, devices, and geography.
  • Product leaders and management get a number that survives standups, retros and review sessions without the need for translation.
  • SEO and marketers get a metric that tracks Core Web Vitals, which Google uses for search ranking, and gets to understand full user experience journeys.
  • Owners and executives get a top-line metric that provides context to NPS, retention, and conversion metrics.

Put user experience in focus#

If you’re not looking at your site this way yet, you can start today.

Calibre customers can find UX Rating on RUM Dashboard & Audience reports. If you’re not a Calibre user, sign up for a free trial and check it out or learn more about UX Rating in our docs. It’s the best way to get a quick pulse on how your users are doing.

Ben Schwarz

Ben Schwarz

Ben is the Founder and CEO of Calibre. He uses his experience in far-reaching Open Source projects and web standards to build tools for a better, more accessible web. Find him on Bluesky Mastodon or LinkedIn.