How to speed up your WordPress site: a plain-English fix guide

Why WordPress sites slow down

WordPress is flexible, which is one reason it powers over 40% of the web. But that flexibility comes at a price. Themes load dozens of scripts and stylesheets. Plugins add more. Every page request runs PHP code, queries a database, and assembles a response from scratch. Without caching or any optimisation, even a modest blog can feel sluggish.

The most common culprits are:

• Unoptimised images — photos uploaded straight from a phone or camera at 5MB each, displayed at 300 pixels wide
• No page caching — every visitor triggers a fresh database query instead of being served a pre-built HTML file
• Cheap shared hosting — your site shares server resources with hundreds of others; when they're busy, you're slow
• Too many plugins — each one adds weight, and some load scripts on every page regardless of whether they're needed
• No content delivery network (CDN) — your files are served from one location, often far from your visitors

None of these are unusual. They're just the natural state of a WordPress site that hasn't been tuned. This guide works through each one in order of impact.

Measure first: PageSpeed Insights and GTmetrix

Before you change anything, get a baseline score so you can measure whether your changes are actually working. Two free tools are worth bookmarking.

Google PageSpeed Insights (search "PageSpeed Insights") tests your URL against Google's real-world data and gives you a score from 0 to 100 for both mobile and desktop. Crucially, it tells you which specific issues are dragging your score down, listed by estimated impact. This is your primary source of truth because Google uses the same signals for search rankings.

GTmetrix (gtmetrix.com) gives a more detailed waterfall view, showing exactly which files are loading, in what order, and how long each one takes. It's particularly useful for spotting render-blocking scripts and oversized images.

Hosting: the biggest factor most ignore

No amount of optimisation can fully compensate for genuinely slow hosting. If your server takes 1.5 seconds just to respond to a request before the browser has even started loading anything, you're starting from behind.

Most small business owners in the UK start on shared hosting at around £3 to £8 a month. This is fine when your site is new and low traffic. As your site grows, you'll notice it. The tell-tale sign is a high "Time to First Byte" (TTFB) in GTmetrix, typically over 600ms.

If your PageSpeed score is poor and your TTFB is consistently high, no amount of caching plugins will fix it completely. The options are:

• Move to a managed WordPress host — providers like Kinsta, WP Engine, or Cloudways are built specifically for WordPress and include server-level caching. They typically start at £25 to £40 a month, which is worth it once your site is generating revenue.
• Upgrade your plan with your existing host — most hosts offer a VPS or cloud option with dedicated resources. Ask your host what your current TTFB is and what a higher plan would look like.

Caching plugins: the highest impact per minute of effort

Caching is the single most effective thing you can do for a WordPress site on a limited budget. Instead of building each page from scratch every time someone visits, a caching plugin saves a pre-built HTML copy and serves that instead. The difference is often dramatic: a page that took 3 seconds drops to under a second.

The main options are:

Image optimisation: compression, lazy loading, and WebP

Images are typically the biggest files on any web page, and they're almost always the biggest opportunity for improvement. A photo uploaded directly from a phone at its original size might be 4MB or more. The same image, properly optimised, can be under 100KB with no visible quality difference to the human eye.

Compression

Two plugins make image compression straightforward:

WebP conversion

WebP is a modern image format that produces smaller files at the same visual quality as JPEG or PNG. Chrome, Firefox, and Safari all support it. Both Smush and ShortPixel can convert your images to WebP and serve them to browsers that support it, with fallbacks for any that don't.

Lazy loading

Lazy loading means images below the fold (below what's visible on screen when the page first loads) are not fetched until the visitor scrolls to them. WordPress has had native lazy loading built in since version 5.5, so you may already have this. WP Rocket and LiteSpeed Cache both extend this to other media types too.

Removing bloat: unused plugins and render-blocking scripts

Every active plugin on your WordPress site adds weight, even if you rarely use it. Some plugins load JavaScript or CSS files on every single page, even pages where they do nothing at all. A contact form plugin that loads its scripts on your homepage is wasted load time.

Audit your plugins

Go to Plugins in your WordPress dashboard and look critically at each one. Ask yourself whether it's genuinely active and necessary. Common culprits to consider removing:

• Social sharing buttons from old providers
• Page builder plugins for page builders you no longer use
• Sliders and carousels (almost always slower than a static image)
• Abandoned plugins with no recent updates
• Duplicate functionality covered by another plugin

Render-blocking scripts

GTmetrix and PageSpeed Insights will flag any scripts that are blocking the page from rendering. This usually means a JavaScript file that loads in the page head and forces the browser to wait before displaying anything. WP Rocket's "Delay JavaScript Execution" feature handles this automatically. LiteSpeed Cache has an equivalent setting under the "Page Optimisation" tab.

You can also check which scripts your theme is loading unnecessarily. Tools like Query Monitor (a free plugin) show you exactly which scripts fire on each page.

CDN: Cloudflare free tier

A content delivery network (CDN) stores copies of your static files (images, CSS, JavaScript) on servers around the world. When someone in Edinburgh visits your site, they get files from a nearby server rather than wherever your web host is based. This reduces latency significantly, particularly for overseas visitors.

Cloudflare offers a genuinely useful free tier that covers CDN, DNS management, and basic DDoS protection. Setting it up means changing your domain's nameservers to point to Cloudflare. Once done, Cloudflare sits between your visitors and your hosting server and caches your static content automatically.

1. Create a free account at cloudflare.com
2. Enter your domain. Cloudflare will scan your existing DNS records.
3. Review the records it found and confirm they look correct
4. Log into your domain registrar and update the nameservers to the two Cloudflare gives you
5. Propagation takes anywhere from a few minutes to 24 hours. Once active, Cloudflare starts caching your content automatically.

Database optimisation

WordPress stores everything in a MySQL database: posts, pages, settings, plugin data, and a growing pile of revisions. Over time this database accumulates clutter. Post revisions alone can number in the thousands on an active site. Transients (temporary data stored by plugins) pile up. Old spam comments stay in the table.

A bloated database makes every database query slightly slower, which adds up across an entire page load.

Clean it up

WP-Optimize is a free plugin that handles most of this in one place. It can remove post revisions, clear out spam and trashed comments, remove expired transients, and run an OPTIMIZE TABLE query to defragment the database tables. LiteSpeed Cache also includes a database optimisation tab if you're already using it.

1. Install WP-Optimize (or use LiteSpeed Cache's database tab if you have it)
2. Take a database backup first using your host's backup tool or UpdraftPlus
3. Select the clean-up options: revisions, trash, spam, transients
4. Run the optimisation

You can also limit how many revisions WordPress saves going forward by adding a single line to your wp-config.php file:

Core Web Vitals: common WordPress failures and fixes

Google's Core Web Vitals are a set of real-world performance metrics that affect your search rankings. There are three main ones, and WordPress sites fail them in predictable ways.

Largest Contentful Paint (LCP)

LCP measures how long it takes for the largest visible element on the page (usually the hero image or main heading) to appear. The target is under 2.5 seconds. WordPress sites fail this most commonly because:

• The hero image is not preloaded. WP Rocket and LiteSpeed Cache both have a "preload critical images" or "LCP preload" setting. Enable it.
• The image is too large. A full-width hero should typically be under 150KB for a JPEG. Use Smush or ShortPixel to compress it.
• The server responds slowly. Go back to the hosting section if your TTFB is the bottleneck.

Cumulative Layout Shift (CLS)

CLS measures how much the page jumps around as it loads. A score above 0.1 means your page is visually unstable, which Google penalises. On WordPress sites the common causes are:

• Images without dimensions — if your theme or page builder doesn't set a width and height on image elements, the browser doesn't know how much space to reserve, and the layout shifts when the image loads
• Web fonts loading late — if your fonts take a moment to load, text reflows when they arrive. Use the font-display: swap CSS property, which most modern themes support
• Ads and embeds — anything that loads asynchronously and pushes content down

Interaction to Next Paint (INP)

INP replaced First Input Delay (FID) in 2024 as a Core Web Vitals metric. It measures how quickly your page responds when someone interacts with it (clicks a button, taps a menu). The target is under 200ms. WordPress sites tend to fail this when too much JavaScript is running on the main thread. The fix is usually reducing or deferring third-party scripts, particularly chat widgets, tracking pixels, and marketing tools.