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Lighthouse 6 update, bookmark & compare, and JavaScript frustration

Jun 1, 2020

Hi there,

Another month, another batch of fresh features and stories to share! Over the past few weeks, we've been rolling out new metrics and features to help you focus on tracking what matters most on your pages – and quickly troubleshoot when things change. 

Keep reading to learn more about our newest JS metrics, "bookmark and compare" functionality, Web Vitals support, and quick guide to understanding averages, medians, and percentiles.

We've got more exciting stuff in the works. Stay tuned!

Until next time,


Lighthouse 6 update

On 1 July 2020, we'll be rolling out updated test agents. Among other things, this means that Lighthouse will be updated from version 5.6.0 to 6.0.0, and Lighthouse test runs will use the official throttling settings for mobile and desktop.

While we can't predict exactly how the updates will affect your metrics, here are a couple of observations we've made:

  • Lighthouse performance scores for mobile tests stay roughly the same.
  • Lighthouse performance scores for desktop tests should be much higher. This is due to changes in throttling. SpeedCurve used the default mobile throttling for all tests in Lighthouse 5.6. Desktop tests in Lighthouse 6.0 now use a much faster network connection.

New! Compare ALL the things!

We've made it easy for you to bookmark and compare different Synthetic tests in your test history. Now you can generate side-by-side comparisons that let you not only spot regressions, but easily identify what caused them.

We're already getting great feedback – such as this tweet by performance consultant Harry Roberts – that this new feature is doing exactly what it's meant to do: simplify and speed up the process for tracking issues and regressions.

Are your JavaScript long tasks frustrating your users?

When it comes to JavaScript tasks, how long is too long? Mark (@MarkZeman) shares why we've recently added a trio of new JavaScript CPU metrics to help you understand if your scripts are blocking the main thread and getting in the way of a smooth experience for your users:

  • Long Tasks
  • Number of Long Tasks
  • Longest Task

Not only can you track these metrics for the full page load, you can also split them out by first-party or third-party attribution, so you know exactly where the responsibility for a janky page lies. For any of your request groups, you can track long task time and set a performance budget to keep your own first-party components or any third parties honest. Pretty sweet!

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

We recently added the ability for you to filter your data at the 75th percentile. This raises the question: How do you choose between average, median, 75th percentile, and 95th percentile? To help answer that question, Joseph (@Joseph_Wynn) wrote up this handy guide.

ICYMI: Web Vitals will become a key SEO factor

In May, Google announced that Core Web Vitals will become an important search ranking factor. In this short video, Cliff (@cliffcrocker) explains how to create a Web Vitals dashboard in SpeedCurve, and then set up performance budgets and alerts for both LUX and Synthetic monitoring.

GOV.UK success story!

Matt Hobbs recently shared how his team at GOV.UK removed the shard domain for critical assets. Not only did they see improvement across key performance metrics, they're also now able to make the most of HTTP2 features. Win! 

A/B testing with Netlify and SpeedCurve

Performance consultant Tim Kadlec demonstrates how to run an A/B test using Netlify and LUX, our RUM tool. Tim's demo shows that the test setup was not only fast, but started to show impact almost immediately:

"Without spending much time at all, I was able to get a split test up and running so I could see the impact was having."

Do you have stories or feedback to share?

We love sharing what our users are doing and learning! If you've written a blog post, recorded a video, or even just posted some screenshots on social media – we'd love to see it. You can reply directly to this email, or give us a shout on Twitter (@SpeedCurve).