Speed & Core Web Vitals
The metrics Google measures on real visitors, what slows a page down and how to make it fast.
Guides
- Speed13 min read
PageSpeed score: how to read it and what counts as good
A PageSpeed score is a 0-100 summary of five lab metrics from one simulated visit on a phone: 90 or more is good, 50-89 needs improvement, under 50 is poor. Here is what the number means, why it moves and what to fix first.Updated 15 Oct 2026 - Speed16 min read
Reading a waterfall chart and filmstrip: where the seconds go
A request waterfall shows every file a page loads and when; the filmstrip shows what the visitor saw meanwhile. Learn the anatomy of a bar, the six patterns behind most slow pages, how to match frames to metrics, and what to fix first.Updated 15 Oct 2026 - Speed14 min read
HTTP/2 vs HTTP/1.1: multiplexing, header compression and what changes for your site
HTTP/2 vs HTTP/1.1: HTTP/2 sends every file of a page over one connection at once and compresses headers, where HTTP/1.1 queues files six at a time. What changes, what does not, and what happened to server push.Updated 4 Oct 2026 - Speed12 min read
PNG vs JPG (JPEG): which to use for photos, graphics and transparency
PNG vs JPG comes down to the picture: JPG (JPEG) for photos, PNG for graphics with sharp edges, text or transparency. How each format works, when each wins and what to use on a website today.Updated 4 Oct 2026 - Speed14 min read
What is a CDN? What it fixes for speed, and what it does not
A CDN (content delivery network) is a set of servers around the world that keep copies of your files and answer each visitor from the nearest one. What that speeds up, what it cannot, and how to set one up without caching the wrong pages.Updated 4 Oct 2026 - Speed19 min read
HTTP/2 and HTTP/3 explained: what they change for speed and how to turn them on
HTTP/2 loads every file of a page over one connection at once; HTTP/3 does the same over QUIC with a faster handshake. What each changes, how to check yours and how to turn them on.Updated 28 Sept 2026 - Speed11 min read
AVIF vs WebP vs JPEG: the best image format for the web
AVIF vs WebP: AVIF usually makes photos smaller at the same look, WebP encodes faster and is the safer all-rounder, and JPEG is still fine in a few places. Which format for which image, the quality settings that work, and how to serve a fallback.Updated 27 Sept 2026 - Speed21 min read
Core Web Vitals explained: LCP, INP and CLS, thresholds and how to pass
Core Web Vitals are three Google metrics for how a page feels to real visitors: loading (LCP), responsiveness (INP) and visual stability (CLS). What each measures, the thresholds and how to pass.Updated 27 Sept 2026 - Speed12 min read
Cumulative Layout Shift (CLS): what it is and how to fix it
Cumulative Layout Shift scores how much a page jumps while you use it; good is 0.1 or less. Find the element that moves, then reserve its space with width and height, aspect-ratio or a fixed slot. Covers images, ads, embeds, banners and fonts.Updated 27 Sept 2026 - Speed14 min read
First Contentful Paint and Speed Index: what they measure and what moves them
First Contentful Paint (FCP) is the moment the first text or image appears; Speed Index is how quickly the rest of the screen fills in. What each measures, good values, how they relate to LCP, and the fixes that move them.Updated 27 Sept 2026 - Speed14 min read
font-display: swap, preload and self-hosting: web fonts without layout shift
font-display: swap shows text at once in a fallback font instead of hiding it while the web font downloads. Add it, preload two fonts, self-host and subset them, and tune the fallback so nothing jumps.Updated 27 Sept 2026 - Speed14 min read
How to choose a web host: compare measured speed, not reviews
How to choose a web host: pick a data centre near your visitors, match the plan type to your site, then compare cached and uncached TTFB of your own site on each candidate and the field data of sites already there.Updated 27 Sept 2026 - Speed12 min read
How to lazy load images (and iframes) without hurting LCP
To lazy load images, add loading="lazy" to every image and iframe below the first screen, never to the hero, and give each one width and height. What to lazy-load, what never to, and how WordPress and plugins handle it.Updated 27 Sept 2026 - Speed15 min read
How to reduce TTFB: fix a slow server response time
To reduce TTFB, remove redirect hops, serve pages from a page cache, then speed up what the cache cannot cover (slow plugins and queries, outbound calls, cron, old PHP) before you pay for a bigger plan.Updated 27 Sept 2026 - Speed13 min read
Interaction to Next Paint (INP): what it is and how to improve it
Interaction to Next Paint measures how quickly a page reacts to taps, clicks and key presses; good is 200 ms or less. Learn why it replaced FID, how to find the slow interaction, and how to fix it by breaking up long tasks and trimming scripts.Updated 27 Sept 2026 - Speed14 min read
Largest Contentful Paint (LCP): what it is and how to improve it
Largest Contentful Paint is the time until the biggest image or text block on screen is drawn; good is 2.5 s or less. Find your LCP element, see which of its four parts is slow, and fix them in the order that pays off most.Updated 27 Sept 2026 - Speed14 min read
Lighthouse score: what it measures and why 100 does not mean fast
The Lighthouse score is a weighted blend of five lab metrics from one simulated page load. Learn how it is calculated, how it differs from PageSpeed Insights and Core Web Vitals, and whether it affects SEO.Updated 27 Sept 2026 - Speed12 min read
The best image size for a website: pixels and file weight for every slot
The best image size for a website is the width the image is displayed at, times two for sharp screens: about 1600-2000 px for a full-width hero, 1200-1600 px for content images and 2× the slot for thumbnails, at under 100-300 KB each.Updated 27 Sept 2026 - Speed13 min read
Total Blocking Time: find the long tasks and cut main-thread work
Total Blocking Time adds up how long JavaScript froze the page during load. Find the long tasks behind it, then remove, defer, split and offload the work until TBT is under 200 ms.Updated 27 Sept 2026 - Speed22 min read
TTFB (time to first byte): what it is, what is good and how to fix it
TTFB (time to first byte) is the wait between requesting a page and the first byte of the answer. What it includes, what a good TTFB is, how to measure it and how to fix a slow server.Updated 27 Sept 2026 - Speed10 min read
async vs defer: loading JavaScript without blocking the page
async and defer both download a script without blocking the page, but defer runs scripts in order after the HTML is parsed, while async runs each one as soon as it arrives. When to use which, how modules and inline scripts behave, and how to defer JavaScript in WordPress.Updated 26 Sept 2026 - Speed13 min read
Core Web Vitals and SEO: how much do they affect rankings?
Core Web Vitals are part of how Google ranks pages, but a small part: relevance comes first, and good scores never guarantee the top spot. What Google says, and how to act on it.Updated 26 Sept 2026 - Speed14 min read
Does web hosting affect SEO? Location, speed and uptime explained
Hosting affects SEO through speed and availability, not through where the server is: Google does not rank a site by its server country, but a slow or unreliable host hurts Core Web Vitals, crawling and visitors.Updated 26 Sept 2026 - Speed12 min read
ERR_HTTP2_PROTOCOL_ERROR: what it means and how to fix it
ERR_HTTP2_PROTOCOL_ERROR means an HTTP/2 connection between the browser and the site broke mid-response. The quick fixes for visitors, and how site owners find and fix the server-side cause.Updated 26 Sept 2026 - Speed11 min read
ERR_QUIC_PROTOCOL_ERROR: what it means and how to fix it
ERR_QUIC_PROTOCOL_ERROR means the browser's HTTP/3 connection over QUIC failed. The quick fixes for visitors, and how site owners find the network or server cause and keep visitors on a working connection.Updated 26 Sept 2026 - Speed14 min read
How important is page speed for SEO? What Google has said since 2010
Page speed is a real but modest Google ranking factor: it helps between pages of similar relevance and never beats a better answer. What Google measures, what else speed changes for search, and when it is worth the work.Updated 26 Sept 2026 - Speed12 min read
How to enable HTTP/2 and HTTP/3 on nginx, Apache, Caddy and Cloudflare
How to enable HTTP/2 and HTTP/3: the exact nginx, Apache, Caddy, LiteSpeed, IIS and Cloudflare settings, the firewall rule HTTP/3 needs, and how to check that browsers really use them.Updated 26 Sept 2026 - Speed14 min read
How to improve Core Web Vitals and pass the assessment
How to improve Core Web Vitals: find the metric and template that fail in the field, fix the usual cause of each (LCP, INP, CLS) in the right order, and confirm the pass over 28 days.Updated 26 Sept 2026 - Speed12 min read
How to reduce image file size without losing visible quality
To reduce image file size, resize the image to the pixels you need, compress it at a sensible quality and save it in an efficient format. The steps, the settings and the free tools, on any computer.Updated 26 Sept 2026 - Speed21 min read
Image optimization for the web: size, format, compression and loading
Image optimization means sending each visitor the smallest image file that still looks right, at the right moment. The four levers, the order to use them and the tools to check.Updated 26 Sept 2026 - Speed12 min read
Lossy vs lossless compression: which to use for each image
Lossy compression makes images much smaller by discarding detail you are unlikely to see; lossless compression keeps every pixel and saves less. How each works, which formats use which, and when to choose one over the other.Updated 26 Sept 2026 - Speed27 min read
Page speed: what it is, why it matters and how to make your site faster
Page speed is how quickly a page shows its content and responds to visitors. What the numbers mean, what a good result is, how to test it and the fixes that help most.Updated 26 Sept 2026 - Speed22 min read
Render-blocking resources: the CSS, JavaScript and fonts that delay your page
To eliminate render-blocking resources, defer the scripts in head, inline the CSS the first screen needs, load the rest later and drop code the page never uses.Updated 26 Sept 2026 - Speed13 min read
What is a good page load time? Targets in seconds, and how to measure
A good page load time means the main content is visible within 2.5 seconds on a phone, the page reacts to taps within 200 ms and nothing jumps, for at least 75 % of visits. The targets per metric and how to measure yours.Updated 26 Sept 2026 - Speed10 min read
What is a WebP file? How to open, convert and use one
A WebP file is an image in Google's WebP format, which stores photos and graphics in fewer bytes than JPEG or PNG. What it is, why you keep getting them, how to open or convert one, and WebP vs JPG and PNG.Updated 26 Sept 2026 - Speed10 min read
What is an AVIF file? How to open, convert and use one
An AVIF file is an image in the AV1 Image File Format, which compresses photos further than JPEG and often further than WebP. What it is, how to open or convert one, browser support and when to use it.Updated 26 Sept 2026 - Speed13 min read
What is QUIC? The protocol under HTTP/3, compared with HTTP/2
QUIC is the transport protocol under HTTP/3: it runs over UDP, sets up the connection and encryption in one round trip and keeps a lost packet from stalling the whole page. How it works and when HTTP/3 beats HTTP/2.Updated 26 Sept 2026 - Speed17 min read
Why is my website slow? How to find the cause and fix it
A slow website almost always comes down to a slow server, heavy images, render-blocking files, too much JavaScript or layout shifts. How to tell which one you have from a speed test, and the fix for each.Updated 26 Sept 2026 - Speed13 min read
Core Web Vitals for e-commerce: product and category pages
Where shops fail LCP, CLS and INP on product pages, category grids and checkout, with the fix for each template, the WooCommerce and Shopify settings behind them, and how to measure per template.Updated 25 Sept 2026 - Speed14 min read
Core Web Vitals for news and publisher sites: ads, embeds and CLS
Publishers fail Core Web Vitals their own way: unreserved ad slots, banners that push content, embeds that resize, ad tech on the main thread. The fix for each, with code and a per-template checklist.Updated 25 Sept 2026 - Speed14 min read
Core Web Vitals history: reading 40 weeks of real-user data
A speed test shows how a page performs today. Forty weeks of Chrome UX Report data show when it changed, so you can find the update, plugin or image behind a drop and know when a fix has landed.Updated 25 Sept 2026 - Speed13 min read
Critical CSS: is it still worth doing in 2026?
Critical CSS inlines the styles for the first screen and loads the rest later. Learn when it still pays, what it costs to maintain, the simpler fixes to try first and how to measure the difference.Updated 25 Sept 2026 - Speed12 min read
DOM size: why 3,000 nodes is a problem and how to shrink a page
A page with thousands of HTML elements is slow to style, lay out and react to taps. Find where the nodes come from, count them yourself, and cut them with builder settings and content-visibility.Updated 25 Sept 2026 - Speed13 min read
Field data vs lab data: why PageSpeed and Search Console disagree
Lab data is one throttled test run; field data is 28 days of real Chrome visitors. Why the two disagree, which one Google ranks with, and what to do in each of the four combinations.Updated 25 Sept 2026 - Speed14 min read
Image CDNs and on-the-fly resizing: URL parameter or build step?
An image CDN resizes and converts to WebP or AVIF from a URL parameter, so one master serves every screen. What the services cost, the URL patterns, the pitfalls, and when a build step is enough.Updated 25 Sept 2026 - Speed13 min read
Mobile vs desktop scores: why mobile is always lower and what to do
The same page scores 95 on desktop and 55 on mobile because the mobile test simulates a slow phone on a slow network. What is simulated, why Google uses the mobile number, and what to fix first.Updated 25 Sept 2026 - Speed12 min read
Preload, preconnect, prefetch: which resource hint when
Resource hints tell the browser what to fetch before it would find out on its own. One hint per job, the exact syntax for images, fonts and scripts, and the mistakes that make hints slower than none.Updated 25 Sept 2026 - Speed13 min read
Responsive images: srcset and sizes explained with real numbers
Stop sending a 2000-pixel photo to a 400-pixel slot. How the browser picks from srcset, why sizes is required, and a three-breakpoint example with the real pixel counts, on any CMS.Updated 25 Sept 2026 - Speed12 min read
Service workers and offline pages: the minimal safe version
A service worker does nothing for a first visit and can serve stale pages for weeks. The minimal recipe: network-first HTML, cached hashed assets, an offline page, a kill switch, and when to skip it.Updated 25 Sept 2026 - Speed14 min read
Speed budgets: setting one and holding to it in CI
Pick a speed budget from your own numbers, write it into the repo and make the build fail when a pull request breaks it, with Lighthouse CI configs and a budgets.json for a shop and a marketing site.Updated 25 Sept 2026 - Speed12 min read
Third-party scripts: taming tag managers, chat widgets and ads
Measure what tag managers, chat widgets, pixels and embeds cost your visitors, then cut it with removal, facades, consent-gated loading and tag manager hygiene, with a budget you can hold to.Updated 25 Sept 2026 - Speed13 min read
Video on landing pages without killing your LCP
Hero videos and YouTube embeds are the fastest way to a 6-second LCP. Learn what counts as the LCP element for video, the poster and facade patterns that keep it under 2.5 s, plus WordPress settings.Updated 25 Sept 2026
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