What is Real User Monitoring (RUM)?

Real User Monitoring (RUM) measures how real visitors experience your website. It captures metrics like Core Web Vitals, page load times, interaction delays, layout shifts, and network conditions directly from the user's browser. RUM helps you understand how your site performs in real-world conditions across different devices, locations, and connection types.

Why should I use Calibre RUM?

Calibre RUM ranks your pages by traffic, shows which elements slow them down, and breaks experience down by device, browser, country and page group. The script is about 9 KB, privacy-first, and you control sampling and retention.

Is Real User Monitoring difficult to integrate?

No. Add one small script to the head of your pages, and data starts appearing within minutes.

Will RUM slow down my website?

No. The script is about 9 KB and runs after the key rendering phases, so its effect on performance is negligible.

Is Calibre RUM privacy friendly?

Yes. Calibre RUM sets no cookies and collects no personal data. A random session identifier is kept in the browser's sessionStorage and removed when the tab closes. You can also turn off collection in the EU and EEA.

How much does Calibre RUM cost?

RUM is included on every plan. Starter includes 5,000 sessions a month, Team includes 10,000 with add-on packs of 100,000, and Company includes 1 million. Sampling lets you control how many sessions you use.

Monitor real user experience at any scale

Calibre RUM helps you understand how fast, usable, and stable your website feels to real people.

The Calibre RUM dashboard with live visitors, sessions, UX Rating and charts for each Core Web Vital

Observe

Find out how your website performs for real people

Collect Core Web Vitals and other key user experience quality signals.

A 9 KB, privacy-first script

Live in minutes. No cookies, no personal data, and almost no effect on page speed.

Learn about Calibre RUM →

You control the cost

Set your own sampling rate and data retention, so the bill is never a surprise.

Learn about sampling →

Beat Slow Pages

Start with your busiest pages

Every page ranked by traffic, and grouped by template.

Ranked by traffic

Fix the pages most visitors see first.

Learn about the Pages Leaderboard →

Grouped by template

Compare product, category, blog or checkout pages as groups, using URL patterns.

Learn about Page Groupings →

Elements

Find the elements that slow pages down

See which element is behind each poor LCP, INP and CLS score.

Slow interactions (INP)

See which buttons, links and inputs keep visitors waiting.

Learn about INP →

Slow main content (LCP)

Find the images and text blocks that take longest to appear.

Learn about LCP →

Layout shifts (CLS)

Find the elements that jump around while the page loads.

Learn about CLS →

Track key elements over time

Name important elements with a data-name attribute and follow them release by release.

Learn about element attribution →

Audience

See where user experience shines and suffers

UX Rating by country, device, browser and more.

UX Rating

The share of visits that were fast, stable and responsive.

Experience around the world

See on a map which countries get a slow site.

Split it any way

Break UX Rating down by country, page, device and browser.

“Calibre’s RUM dashboard was instantly attractive thanks to the negligible impact on page weight, support for CWV, and thoughtful metrics presentation.”