Hi <<First Name>>,
Well... if you keep track of this kind of thing, you may have noticed that there wasn't a May edition of this newsletter. That's because I've had my head down collaborating with the rest of our awesome team on an exciting new initiative: Core MOBILE Vitals
That's right — like Core Web Vitals, but for your native apps! More on that below.
That's not the only thing that's new in the performance and observability community. Keep reading for...
- A performance audit that reduced LCP from 7s to under 2s for Wish.com
- Three visuals that make the business case for performance
- Compelling Shopify research about the impact of LCP slowdowns on conversion rate
- CSS vs JS: Which animation strategy is more performant?
- And more!
If you have any questions or feedback, I'd love to hear from you. And if you have any great resources you think belong in the next edition of this newsletter, please send them my way!
Until next month,
Tammy
@tammyeverts.com
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Core Mobile Vitals: Understand how users feel about your app
One of the greatest strengths of Core Web Vitals is its ability to translate complex performance engineering concepts into metrics that both technical and business teams can understand and act on. Bringing a similar framework to native mobile apps can help organizations align performance, user experience, and business outcomes.
That's why I'm incredibly excited to announce the Core Mobile Vitals initiative. We’ve identified four user-centred goals that we believe Core Mobile Vitals should address: Screen Load, Responsiveness, Smoothness, and Stability. And similar CWV, Mobile Vitals should also meet these requirements:
- Track something the user feels
- Can be measured reliably and consistently
- Supported out of the box across platforms
- Clear, evidence-backed thresholds for ‘good’ and ‘poor’
- Correlates with business outcomes, like conversion, retention, and engagement
This isn't a proprietary initiative. It's a community project. I'd love to hear your thoughts!
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Performance audit: Wish.com
I love these performance audits from Aaron T. Grogg. This time, Aaron investigated Wish.com's high Largest Contentful Paint time, which led him down a rabbit hole of performance paper cuts. But there's a happy ending: he was able to reduce their LCP from 7.12s to 1.67s with just a couple of key improvements — a performance wish come true. (Sorry, I couldn't help it!)
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Make the business case for performance with just three visuals
I’ve spent almost two decades making the case that web performance is not just a technical problem — it's a business problem. Over the years, I keep coming back to the same three data visualizations. If you want to immediately grab people's interest and get them to care about site speed and user experience, these are the charts you need.
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Shopify research: What the data shows about site speed and sales
Speaking of compelling data visualizations, spy the correlation charts in this study from Shopify! Analyzing Core Web Vitals across the entire Shopify ecosystem, Mateusz Krzeszowiak found that every 100ms of additional LCP correlates with a 3.5% drop in conversion — and stores with 2.5s LCP convert roughly 30% worse than stores at 1.5s.
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Theme Vitals: How real-world websites perform for each Shopify theme
If you have a Shopify store (or if you're just nosy, like me), Theme Vitals is a fantastic resource. (Thanks to its creator and maintainer, Sia Karamalegos!) Every month, get the latest web performance data — including Core Web Vitals — for sites using each Shopify theme.
(Speaking of themes, you may have noticed a few themes running through this newsletter: Core Vitals, Shopify, business impact, and large datasets!)
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CSS vs JS: The performance implications of different animation strategies
If you've ever wondered whether to reach for an animation library or just write CSS, this investigation by Josh Comeau is a good place to start. The conventional wisdom is that CSS animations are faster than JavaScript ones. That's basically true, but not for the reasons many people assume. Josh walks through the real reason (main thread contention), and then adds an interesting wrinkle: some JS libraries, like Motion, sidestep this problem entirely by using the Web Animations API under the hood.
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Web Performance Week wrap-up
Web Performance Week is a wrap! If you attended, thank you! It was wonderful to see how many folks signed up and turned out.
If you missed it, WPW was a free virtual mini-conference focused on the latest and greatest in web performance and frontend observability — from Core Web Vitals to debugging user experience issues in production.
But no need for FOMO: All the recordings and posts are now available on the Web Performance Week event page.
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Early tickets for performance.now() are available
You know what's even more fun than a virtual conference? An in-person conference! The sixth edition of performance.now() is happening in Amsterdam on November 19-20. That sounds far away, but start planning early to get your early-bird price while tickets are still available. (After June 30, ticket prices go up in stages.) This is hands-down my favourite event of the year. I hope to see you there!
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