1. **[Core Web Vitals, the metrics](https://web.dev/articles/vitals):** Largest
Contentful Paint, Interaction to Next Paint, and Cumulative Layout Shift.
These metrics are platform agnostic and defined in a spec that any other
browser is free to implement. [Firefox already
has!](https://bugzilla.mozilla.org/show_bug.cgi?id=1722322)
2. **[The Chrome User eXperience Report
(CrUX)](https://developer.chrome.com/docs/crux):** The public dataset used by
Google as a ranking signal for SEO. This is specific only to Chrome, so any
other browser—including Chrome on iOS!—is a blind spot.
These two points yield two corresponding problems…
1. Apple haven’t implemented any of the Core Web Vitals in their own browser,
Safari, and;
2. Apple, until [iOS
17.4](https://developer.apple.com/support/alternative-browser-engines/),
hasn’t allowed any non-WebKit browser engine on the iOS platform.
This means that we’ve had zero visibility of the Core Web Vitals metrics on iOS
or any flavour of Safari at all. If you’re based in [North
America](https://gs.statcounter.com/browser-market-share/mobile/united-states-of-america)
or northwestern Europe, that may mean **the majority of your audience is
completely unaccounted for**.
However, things are about to change.
Beat the Competition
## Core Web Vitals Come to Safari
Apple announced that Largest Contentful Paint and Interaction to Next Paint
will be coming to Safari as part of [the Interop 2025
project](https://webkit.org/blog/16458/announcing-interop-2025/)! This means
that we can begin tracking and instrumenting two of the three Core Web Vitals
before the end of the year!
## Are You Prepared?
If you’ve been focusing on Core Web Vitals for your Chrome visitors already,
you’re well poised. But are you prepared for what it might mean for the
business? Are your developers prepared for the different rendering engine? Do
you know how to track site-speed in Safari if the data doesn’t go into CrUX?
## Get the Workshop
To help prepare clients—both new and old—I’ve designed a one-day workshop
covering, but not limited to:
* **Apple, Safari, and Core Web Vitals**
+ Why can’t we get Core Web Vitals on iPhones?
+ Why can’t we get Core Web Vitals in Safari?
+ What even is Chrome on iOS?
* **Key events**
+ LCP is coming to Safari in 2025!
+ Blink can run on iOS as of 17.4 (but it still doesn’t)
* **What does Safari mean to you?**
+ Based on your own audience, how much does it matter to you?
+ Can we infer anything from existing Core Web Vitals data?
* **How does Safari differ from Chrome?**
+ WebKit vs. Blink
+ JavaScriptCore vs. V8
+ Performance API availability
+ Interop 2025
* **Do the same optimisation techniques apply?**
+ Can we reuse the same work we did for Chrome?
+ Do we need to do anything differently?
+ Does Safari need special treatment?
* **How do we measure Safari in the wild?**
+ If it’s not in CrUX, where is it?
+ Real user monitoring
+ Which metrics can we capture
* **Safari on localhost**
+ Safari-specific devtools
+ Tips, tricks, and workflows
+ Testing real devices
The goal is to leave the team aware of the upcoming changes, arm them with tools and knowledge to optimise for the different engines, and ensure that your Safari users aren’t being overlooked. ### Remote or In-Person I much, much prefer in person workshops—it means we can hang out and probably head for drinks after! But as it’s only a single day, running the workshop remotely works pretty naturally. Remote workshops will be recorded for you to keep. Ready? [Let’s get it booked in!](/contact/) Arrange the WorkshopHarry gave the team a strong footing for identifying performance issues on iPlayer. With his knowledge, we were able to roll out quick fixes to our audiences without the need for big rewrites, all within just two days.
— Matthew Burrows, BBC iPlayer