Google’s Core Web Vitals are useful user-experience measurements: Largest Contentful Paint (LCP) should be 2.5 seconds or less, Interaction to Next Paint (INP) should be 200 milliseconds or less, and Cumulative Layout Shift (CLS) should be 0.1 or less. These are diagnostic targets, not a promise of higher rankings. Start with PageSpeed Insights or Lighthouse, and test important pages on mobile as well as desktop.
1. Large, unoptimized images
Large images are a frequent cause of slow pages. A full-size photo uploaded straight from a phone or camera can be several megabytes, even when it appears small on screen.
How to fix it: Resize images to the largest dimensions they will actually display, compress them, and use modern formats such as WebP or AVIF where supported. Use responsive image sizes so mobile devices do not download desktop-sized files. Lazy-load images further down the page, but do not lazy-load the main image that appears first; it may be the page’s LCP element.
2. Too many plugins, scripts, or theme features
Plugins and third-party tools can add files and requests to every page. Analytics, chat widgets, advertising tags, page builders, sliders, and social embeds can all contribute. The issue is not simply the number of plugins; it is the work they make the browser and server do.
How to fix it: Use the browser’s network panel or a performance report to find slow or unnecessary requests. Remove tools you no longer use, and replace overlapping plugins with one suitable option. Change one thing at a time and retest. If WordPress is your headless CMS, check both the WordPress API response and the public frontend; improving one does not automatically fix the other.
3. Caching is missing or misconfigured
Without caching, a site may repeatedly build the same page from its database for every visitor. Browser caching can also make returning visits slower by forcing assets to download again.
How to fix it: Configure page caching for public pages, browser caching for static assets, and object caching if your platform and hosting support it. A CDN can serve static files closer to visitors. Avoid running multiple cache systems that conflict. After changing a page or its settings, clear the relevant caches and verify the updated version is visible.
4. Slow server response or overloaded resources
If the server takes a long time to send the first byte, image compression alone will not solve the delay. High database load, limited PHP workers, an overloaded server, or an inefficient request can affect the time to first byte (TTFB).
How to fix it: Compare TTFB across several tests and pages. Check that your WordPress, theme, and plugins are supported by your PHP version. Review server and application logs for slow requests. Ask your hosting provider about resource usage, PHP workers, database performance, and available object caching. Test from your audience’s region as well as from a nearby data center.
5. Render-blocking CSS, JavaScript, and fonts
Some files must load before a browser can show or respond to a page. Large stylesheets, scripts loaded too early, and multiple font files can delay the visible content or make the page feel unresponsive.
How to fix it: Remove unused CSS and JavaScript where practical, defer nonessential scripts, and limit third-party embeds. Load only the font weights you use and consider a system font for less critical text. Retest key interactions after each change; delaying a script can break menus, forms, or checkout features if the page depends on it.
A simple website speed checklist
- Test your homepage and key landing pages with PageSpeed Insights on mobile.
- Fix the largest image and script issues first.
- Check caching, server response time, and mobile layout.
- Retest after each major change and confirm forms, menus, and checkout still work.
Website speed work is most effective when it follows evidence. Measure a real page, fix the biggest bottleneck, and measure again. The right fix may be a smaller image, a removed script, better caching, or a server-side change—so diagnose before spending money on a new plan.