SEO

PageSpeed

Q: What is PageSpeed and why does it matter for SEO?

PageSpeed measures how quickly a website loads and becomes interactive. Google has used loading speed as a ranking factor since 2010, and since 2021 it has been bundled into the Core Web Vitals (LCP, INP, CLS). The practical effect: a slow site loses not only ranking points but also conversions — each additional second of loading time costs 7–20 % of the conversion rate.

Q: Is PageSpeed Insights free?

Yes. Google PageSpeed Insights (pagespeed.web.dev) can be used free of charge without registration. It combines Lighthouse lab values with CrUX field data and gives concrete optimisation suggestions. Rankmio pulls the values automatically per project URL into the technical audit.

Q: Which PageSpeed value matters most for SEO?

The LCP value (Largest Contentful Paint) below 2.5 seconds. In addition: INP below 200 milliseconds and CLS below 0.1. These three Core Web Vitals thresholds are hard Google ranking signals — just under them counts as ”good”, well above them lowers the ranking.

Q: How do I improve PageSpeed quickly?

Four quick wins: (1) compress images and use the WebP/AVIF format, (2) audit and minimise third-party scripts (analytics, ads, chat), (3) activate HTTP/2 or HTTP/3, (4) use lazy loading for below-the-fold content. In 90 % of cases, image optimisation alone brings an LCP improvement of 20+ points.

Q: Does PageSpeed differ between mobile and desktop?

Yes, considerably. Mobile PageSpeed is more relevant to Google — since mobile-first indexing (2020) Google primarily evaluates the mobile version. Mobile networks and devices are slower, which is why mobile scores are usually 10–20 points below desktop. Priority for optimisation: mobile first.

Also known as: Page Speed, Loading time, Site Speed, PageSpeed Insights

PageSpeed describes how quickly a web page loads and becomes interactive for the user. Since the Page Experience Update in 2021 it has counted directly as a Google ranking factor as part of the Core Web Vitals (LCP, INP, CLS). At the same time, every serious study (Google Mobile Speed Report 2017, Akamai 2017, Portent 2022) shows that each additional second of loading time typically costs 7–20 % of the conversion rate. That makes PageSpeed one of the few SEO levers that pays into ranking, engagement and conversion at the same time.

The most important PageSpeed metrics

LCP (Largest Contentful Paint) — when is the largest visible element rendered? Target: < 2.5 s.
INP (Interaction to Next Paint) — response time to clicks. Target: < 200 ms.
CLS (Cumulative Layout Shift) — how much does the layout jump around while loading? Target: < 0.1.
TTFB (Time to First Byte) — how quickly does the server respond? Target: < 600 ms.
FCP (First Contentful Paint) — when does the first pixel appear? Target: < 1.8 s.
Speed Index — how quickly is visible content built up?

The biggest PageSpeed killers

Unoptimised images — huge JPEGs/PNGs instead of WebP/AVIF, missing lazy-loading attributes.
Render-blocking JavaScript and CSS — external scripts in the head without async/defer.
Heavy third-party code — tag managers, chat widgets, advertising networks.
Web fonts without font-display: swap — text stays invisible until the font has loaded.
Missing caching — no browser cache, no CDN.
Server response time — a weak host or uncached database queries.

PageSpeed optimisation roadmap

The order with the quickest wins: (1) images to WebP/AVIF + lazy loading + responsive srcset. (2) Minify JS and CSS, remove unused CSS, set JS to async/defer. (3) Web fonts to font-display: swap + preload for the hero font. (4) Activate a CDN + browser cache headers (one year for static assets). (5) HTTP/2 or HTTP/3 + Brotli compression. (6) Server and database optimisation. (7) Inline critical CSS. (8) Review third-party scripts — is all of it really necessary?

Example from practice

Example: a shop has an LCP of 4.8 s (poor), an INP of 290 ms (needs improvement) and a CLS of 0.22 (poor). The conversion rate is 1.8 %. After optimising the three biggest levers (hero image as WebP, lazy loading below the fold, critical CSS inline, web fonts set to swap) the values stand at LCP 2.1 s, INP 180 ms, CLS 0.07 (all three good). Conversion rate after six weeks: 2.7 % — almost +50 %, without anything being changed about the product or the price.

Frequently asked questions

What is PageSpeed and why does it matter for SEO?

PageSpeed measures how quickly a website loads and becomes interactive. Google has used loading speed as a ranking factor since 2010, and since 2021 it has been bundled into the Core Web Vitals (LCP, INP, CLS). The practical effect: a slow site loses not only ranking points but also conversions — each additional second of loading time costs 7–20 % of the conversion rate.

Is PageSpeed Insights free?

Yes. Google PageSpeed Insights (pagespeed.web.dev) can be used free of charge without registration. It combines Lighthouse lab values with CrUX field data and gives concrete optimisation suggestions. Rankmio pulls the values automatically per project URL into the technical audit.

Which PageSpeed value matters most for SEO?

The LCP value (Largest Contentful Paint) below 2.5 seconds. In addition: INP below 200 milliseconds and CLS below 0.1. These three Core Web Vitals thresholds are hard Google ranking signals — just under them counts as ”good”, well above them lowers the ranking.

How do I improve PageSpeed quickly?

Four quick wins: (1) compress images and use the WebP/AVIF format, (2) audit and minimise third-party scripts (analytics, ads, chat), (3) activate HTTP/2 or HTTP/3, (4) use lazy loading for below-the-fold content. In 90 % of cases, image optimisation alone brings an LCP improvement of 20+ points.

Does PageSpeed differ between mobile and desktop?

Yes, considerably. Mobile PageSpeed is more relevant to Google — since mobile-first indexing (2020) Google primarily evaluates the mobile version. Mobile networks and devices are slower, which is why mobile scores are usually 10–20 points below desktop. Priority for optimisation: mobile first.

Used in Rankmio for

PageSpeed and Core Web Vitals audit

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Last updated: 2026-06-17 · Browse all glossary entries