Do Core Web Vitals Actually Matter for SEO?

This deck summarizes the last five years of Core Web Vitals work done on dozens of sites, and answers some of the most common questions:

1. Are Core Web Vitals a ranking factor?
2. What site performance metrics does Google actually care about and how do they measure them?
3. How to interpret Search Console CWV metrics
4. Using WebPageTest to diagnose problems and which you can ignore
5. A summary of things that don't move the needle and which improvements lead to happier users and better rankings.

Presented at BrightonSEO San Diego on 9/23/25 by Matthew Brown (https://mjblabs.com)

Transcript

1. Do Core Web Vitals still matter for SEO/AI Search? Matthew Brown MJBLabs Speakerdeck.com/mjbpdx @MatthewBrownPDX @mjb.bsky.social
2. About Me • I specialize in technical SEO and Product Management. • I primarily work with news and media, B2B, and social networks. • I love technical SEO but sometimes it doesn’t love me.
3. Why are you doing this to me? I could be listening to someone talk about AI right now. Stay with me here.
4. Three reasons Core Web Vitals will still be worth your time
5. One: Core Web Vitals scores aren’t ranking signals
7. Two: What did we learn in the Google leak?
8. It’s Chrome all the way down
9. It’s all about user engagement signals (and look how handsome AI made me!) • CTR • Bounce Rate (Adjusted!) • Time on site • Time per session • Pages per session • Events • Conversions • Good Clicks (session length and event tracking) • BAD CLICKS
10. Three: AI search/retrieval will put a premium on technical SEO AI Crawlers Some don’t execute JS Fast Indexing Any retrieval (RAG) requires you are already indexed Recency Is your content up-to-date?
11. What’s actually important in Core Web Vitals? (I learned the hard way)
12. Three outcomes of CWV work 1. Significant work to improve all CWV metrics with absolutely no change in search ranking 2. Elimination of Poor URLs in GSC that correspond with a ranking improvement 3. It might be the ads
13. Search Console: What means what? LCP (Largest Contentful Paint) How long it takes the page to render the largest visible element. INP (Interaction to Next Paint) How long it takes the page to respond to user interactions. CLS (Cumulative Layout Shift) How much the page UI shifts during page loading.
14. Does Need Improvement really need improvement? Check if competitors are performing better in your niche Balance effort vs. potential gains Are users affected by performance?
15. WARNING: This can lead to the bad place
16. Poor: Your cue to take a hard look
17. Poor + Bad CrUX reports? It’s DEFINITELY time to take a look
18. Use CrUX reports to pinpoint WHEN things went bad
19. Google’s CrUXVis: Easy trending for CWV metrics
20. GSC: Not super helpful!
21. Why I don't love Lighthouse or PageSpeed Insights • Wildly inconsistent “scoring” • Local conditions affect results • Limited network simulation options • Less detailed visualization of problems
22. WebPageTest: Where real work happens
23. Optimal WebPageTest configuration
24. Make sure to preserve the UA string!
25. All the relevant metrics at in one easy visualization
26. The network waterfall
27. Find anything suspect that blocks Document Complete
28. Use Inspect URL in GSC to make sure resources are available to Googlebot and other crawlers
29. Audit the main thread – If it’s blocking it better be important
30. Take a deep breath when you see GTM Audit what’s in GTM – can it use Defer?
31. Remember the Helpful Content Update massacres?
32. Refer back to the Google algorithm leak
34. Could this be the end of JavaScript? https://thenewstack.io/html-first-framework-second-is-javascript-finally- growing-up/
36. Real world results – What has NOT worked • Getting all CWV metrics into the “Good” category • Addressing minor CLS issues • Slight Font/CSS improvements • Slightly improving TTFB • Switching over to WebP • Reducing overall page size
37. Real world results – What’s worked! • Immediately addressing a wave of URLs going into the CWV Poor category • Troubleshoot the bad clicks • Protect the main thread • Investigate ads that block the viewport on scroll
38. Questions? Email: mjb@mjblabs.com LinkedIn: MatthewBrownPDX