Monitor real user experience at any scale
Calibre RUM helps you understand how fast, usable, and stable your website feels to real people.
Track Core Web Vitals, uncover slow pages, diagnose UX issues, and improve performance for every visitor - all with privacy-first, lightweight monitoring.
Observe
Find out how your website performs for real people
Collect Core Web Vitals and other key user experience quality signals.
Sample real user sessions
Calibre captures Core Web Vitals and key UX signals from real browser sessions.
Learn about Calibre RUM →Lightweight, privacy-first script
Start collecting data in minutes. No cookies, no personal data, minimal performance overhead.
Learn more →Control sampling and retention
Set your own session sampling rate and data retention period. Predictable costs, no surprises.
Learn more →Beat Slow Pages
Identify the most highly trafficked pages
Rank them, sort them, group them by template. Fix them.
See how your highest trafficked pages perform
Calibre ranks pages by traffic volume so you can focus on what impacts the most users.
Learn about Pages Leaderboard →Segment by URL section
Define key URL sections for blogs, category, product pages and more
Learn about Page Groupings →Drill into elements
Find problematic elements
With automatic and configurable element targeting, identify & optimise the worst performing elements for LCP, CLS & INP.
See which elements cause long interaction delays (INP)
Find the worst performing interactive elements and optimise them for better user experience.
Learn about INP →See where your pages render slowly (LCP)
Identify the key visual elements that take the longest to load and render.
Learn about LCP →Stop in-page content jitters (CLS)
Find the elements that cause unexpected layout shifts and frustrate users. Optimise for a more stable experience.
Learn about CLS →Track key element performance over time
Follow the performance of key visual and interactive elements over time.
Learn about Element attribution →Audience
See where user experience shines and suffers
UX Rating by Country, Device, Browser, and more.
Good UX %
See how many visitors experienced a fast, stable, responsive site.
Global experience visualised
Get a clear view of how user experiences differ around the world.
Audience, segmented
Group user experience rating by Country, Top Pages, Devices and Browsers.
Why choose Calibre RUM?
Calibre’s focused reports help you make informed decisions that lead to tangible improvements.
Fix the pages that matter most
Every view is ranked by traffic volume. You always know which pages affect the most users and where to focus first.
See exactly which elements are slow
LCP render targets, INP interaction elements, CLS shift sources. Not just metric scores — the specific DOM elements dragging them down.
Segment by anything
Filter by page, device, browser, country, deployment, or URL group. Find where performance is worst and for whom.
Lightweight and tamper-resistant
Minimal performance overhead, no cookies, no personal data collected. The script is secure by default and resistant to supply-chain manipulation.
Predictable costs, no surprises
Control your session sampling rate and data retention period. Scale monitoring to your budget without guessing what the bill will be.
Works alongside CrUX and Synthetic
Combine real user sessions with Google's field data and controlled lab tests for a complete picture of how your site performs.
“Calibre’s RUM dashboard was instantly attractive thanks to the negligible impact on page weight, support for CWV, and thoughtful metrics presentation.”
“Thanks to detailed page breakdowns and filtering, I’ve found performance issues way deeper into customer journeys than I’ve seen before.”
Calibre RUM is built for you
Included on all plans. Set your own sampling rate and retention period — so you control costs from day one.
One platform for all web performance needs
Check first results in just a couple minutes. Start improving performance the same day.
