Speed Optimization
Website speed guides
What slows a website down, what Google measures, and how to fix it, in plain language.
For business owners14 guides
Plain answers on what speed means for your business: how to read a report, what to fix first, what to ask a developer, and how to keep it fast.
- What is website speed optimization?
- How to read a website speed report (for non-developers)
- Which website speed problems to fix first
- Why is my website slow? 15 causes and how to check
- Why is my site slow on phones but fast on a computer?
- Online store speed: a page-by-page plan
- Speed and conversion rate: what the studies say
- Why websites get slower over time
- Speed optimization or a redesign: which do you need?
- Questions to ask before you hire a speed optimizer
- Plugin, host, freelancer or agency: who should fix it?
- Designing for visitors on slow networks and old phones
- How long does speed optimization take?
- Speed checklist before you launch a website
Speed metrics19 guides
What LCP, INP, CLS, TTFB and the other speed numbers mean, which marks count as good, and how to read your own scores.
- Core Web Vitals in 2026: LCP, INP and CLS explained
- What is LCP? How to improve Largest Contentful Paint
- What is INP? Interaction to Next Paint explained
- What is CLS? How to fix Cumulative Layout Shift
- What is TTFB? How to lower Time to First Byte
- What is FCP? How to improve First Contentful Paint
- Total Blocking Time (TBT): what it is, how to lower it
- What is Speed Index? How Lighthouse scores it
- How the Lighthouse performance score is calculated
- Lab data vs field data: why your speed scores differ
- The Chrome UX Report (CrUX) explained
- Does page speed affect Google rankings?
- How to fix a slow LCP, step by step
- How to fix Cumulative Layout Shift, step by step
- How to fix a slow INP, step by step
- How to improve Core Web Vitals: a practical checklist
- Why your PageSpeed score changes between tests
- Page weight and requests: do they matter?
- How does your site compare? Speed benchmarks from 2025
Images, video and fonts12 guides
The heaviest files on most pages. How to pick formats, size images, and load video and fonts without slowing the first view.
- Image optimization for speed: size, format, loading
- Web fonts and speed: how to load them faster
- Lazy loading: when it helps and when it hurts
- Set image width and height to stop layout shift
- Responsive images: srcset, sizes and picture explained
- WebP vs AVIF vs JPEG vs PNG: which image format to use
- Fix layout shift caused by web fonts
- Replace animated GIFs with video
- Video on your website without slowing it down
- SVG for speed: icons, logos and illustrations
- Image SEO and speed: file names, alt text and sizes
- Web fonts in 2025: what real sites do
CSS and JavaScript15 guides
How code slows a page down, and how to load less of it, later, or not at all: render-blocking files, long tasks and outside tags.
- Critical CSS and render-blocking resources explained
- Third-party scripts: how to find and fix the slow ones
- defer, async and module scripts: how scripts load
- Reduce unused JavaScript and CSS: a practical guide
- Resource hints: preload, preconnect, prefetch and more
- Break up long tasks to keep a page responsive
- Reduce main-thread work: where the time goes
- DOM size and rendering: when a page has too much
- CSS performance: size, selectors and rendering cost
- JavaScript bundle size and code splitting
- Remove jQuery and other legacy libraries
- Web workers: moving heavy work off the main thread
- Service workers and speed: caching, and what it costs
- Speculation rules: load the next page before the click
- Hydration and speed in React and Next.js
Servers and caching11 guides
Where the first byte comes from: hosting, caching layers, CDNs and protocols, and how they decide how fast a page starts.
- Caching explained: browser, CDN, page and object cache
- Choosing web hosting for speed: what to look for
- How to reduce server response time (TTFB)
- HTTP caching headers: Cache-Control, ETag and more
- Back/forward cache: making the Back button instant
- Text compression: gzip, Brotli and Zstandard
- What is a CDN and do you need one?
- HTTP/2 and HTTP/3: what changed and how to enable them
- Connection setup: what happens before the first byte
- DNS speed: how name lookups affect your site
- HTTPS and TLS speed: keeping the cost small
WordPress and platforms13 guides
What you can and cannot change on WordPress, WooCommerce, Shopify and site builders, and the fixes that pay off first.
- How to speed up a WordPress website, step by step
- WordPress caching: page, object and browser caches
- Hosting for WordPress speed: what to ask and test
- WordPress themes and plugins: what slows a site
- Elementor, Divi and page builders: the speed cost
- WordPress images: what core does and what you must do
- WordPress database cleanup: what is safe to do
- WooCommerce speed: what to fix first
- WooCommerce checkout speed: a lighter, faster purchase
- Is WordPress slow? What the 2025 data shows
- Shopify speed: what you can change and what to ask
- Wix, Squarespace and Webflow: what you can speed up
- Cloudflare APO for WordPress: how it works
Testing and monitoring10 guides
How to measure speed the right way with PageSpeed Insights, Lighthouse, Search Console and DevTools, and how to catch slowdowns early.
- How to measure Core Web Vitals: tools compared
- PageSpeed Insights explained: how to read your report
- Lighthouse: what it tests and how to run it
- DevTools Performance panel: how to record and read it
- DevTools Network panel: how to read a page load
- WebPageTest and other speed tools: what each is for
- Real user monitoring: measure your own visitors
- Automated speed tests and performance budgets
- Testing on real phones: why it matters and how
- How to test speed changes safely
Technical SEO13 guides
Crawling, indexing, redirects, canonicals, language versions, links, security headers and structured data: the technical side of search that sits next to speed.
- robots.txt, noindex and the tags that control search
- Canonical tags: pointing duplicates to one address
- Redirects and status codes: 301, 302, 404 and 503
- hreflang for English and Spanish versions of a site
- Structured data basics: JSON-LD for small sites
- JavaScript and SEO: what crawlers can see
- Internal links: help visitors and crawlers find pages
- Page titles, descriptions and headings that work
- Mobile-first indexing: what it means for your site
- HTTPS and security headers without the slowdown
- Website migration checklist for speed and search
- AI crawlers, robots.txt and llms.txt
- Do you still need AMP in 2026?
Reference7 guides
Short pages to keep open while you work: the speed glossary, the marks that count as good, caching headers and checklists.
Speed Lab12 guides
Controlled tests on our own pages: one change at a time, measured with Lighthouse, with the method shown so you can repeat them.
- How the Speed Lab tests are run
- Speed Lab: fetchpriority and finding the main image
- Speed Lab: lazy-loading the main image
- Speed Lab: no compression, gzip and Brotli
- Speed Lab: blocking, deferred and async scripts
- Speed Lab: JPEG, WebP and AVIF compared
- Speed Lab: font swap and fallback metrics
- Speed Lab: cookie banners and layout shift
- Speed Lab: content-visibility on a long page
- Speed Lab: inlining critical CSS
- Speed Lab: many small files, HTTP/1.1 and HTTP/2
- Speed Lab: three ways to slow a test down
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Free website audit
Live Google data for any public page: mobile and desktop.
Mobile + desktop · Lighthouse lab test · Real-user Chrome data when Google has it