Understanding Metrics

Diagnose Cumulative Layout Shift (CLS)

How to quickly identify what's causing the biggest layout shifts on your pages

Written by Tammy Everts
Updated over a week ago

Why are my LUX metrics different from those reported by CrUX?

Understanding why your LUX numbers may not match up with the Chrome User Experience Report (CrUX) and what to do about it.

Written by Cliff Crocker
Updated over a week ago

When should I use average, median, and other percentiles?

How to choose between average, median, 75th percentile, and 95th percentile

Written by Joseph Wynn
Updated over a week ago

What do the different SpeedCurve metrics represent?

Glossary of metrics you can track with Synthetic and LUX Real User Monitoring.

Written by Steve Souders
Updated over a week ago

Why are my Lighthouse scores different from my other test results?

Here's why your Lighthouse scores in SpeedCurve might be different from the scores you get elsewhere.

Written by Tammy Everts
Updated over a week ago

Why are my Synthetic and LUX numbers different?

It's quite typical for RUM metrics to be faster than Synthetic. Here's why that is – and why you still need both types of monitoring.

Written by Tammy Everts
Updated over a week ago

Why are the SpeedCurve results different from my other test results?

Here's why. But remember: the most important thing to track is consistency and changes within a single testing tool and settings.

Written by Mark Zeman
Updated over a week ago

Why does my fully loaded time fluctuate so much?

Some pages may have very high or fluctuating fully loaded times. Here's why.

Written by Joseph Wynn
Updated over a week ago

Lighthouse scores and audits

How to find and track your Lighthouse scores and audits.

Written by Tammy Everts
Updated over a week ago

How to remove a single data point from your test averages

If outlier test results are bumping out your averages, here's how to exclude them.

Written by Tammy Everts
Updated over a week ago

Hero rendering times

How we identify the hero rendering metrics, plus how to add element timing.

Written by Mark Zeman
Updated over a week ago

How is Speed Index calculated?

What is the Speed Index score and why does it sometimes not align with your other metrics?

Written by Tammy Everts
Updated over a week ago

Blocking JS & CSS

How SpeedCurve detects blocking JavaScript and stylesheets

Written by Steve Souders
Updated over a week ago

Why don't my charts change when I select median, average, and 75th/95th percentile?

Written by Joseph Wynn
Updated over a week ago

LUX Query Timeouts

How to avoid having LUX queries time out.

Written by Steve Souders
Updated over a week ago

Data Protection & GDPR Compliance at SpeedCurve

Written by Mark Zeman
Updated over a week ago

Time Labels in Charts

What exactly do the time labels in the charts mean?

Written by Steve Souders
Updated over a week ago