Slow WordPress Site? 4 Main Causes + How to Fix Them [2025 Guide]

Your WordPress site is slow? Then you're losing visitors.

You're not alone. 53% of mobile users abandon sites that take more than 3 seconds to load. If your WordPress is slow, you're literally losing opportunities.

The good news? Most speed problems have simple solutions.

In this guide, I'll show you the 4 most common causes that make WordPress slow and, more importantly, how to fix each one with practical solutions that work.

Why Speed Actually Matters

Before we dive into solutions, let me show you why this isn't just a technical issue:

SEO

Google considers speed as a ranking factor since 2021. Core Web Vitals (LCP, INP, CLS) directly influence where your site appears in search results.

Conversions

Sites that load in 1 second have 3x more conversions than sites taking 5 seconds. In e-commerce, each second costs you 7% in sales.

Experience

A slow WordPress = frustrated users. Slow pages increase bounce rate by up to 90%.

Speed isn't a technical detail. It's a business factor.

Diagnose First

Before optimizing, you need to know where you stand. Test your site with this tool:

Google PageSpeed Insights (https://pagespeed.web.dev/)

• Mobile and desktop analysis
• Real Core Web Vitals
• Specific recommendations
• Technical analysis
• Loading waterfall

2025 benchmarks:

• ✅ Excellent: < 2 seconds
• ⚠️ Acceptable: 2-4 seconds
• ❌ Slow: > 4 seconds

1. Too Many Plugins (or Poorly Optimized Ones)

Plugins are what make WordPress powerful, but also what makes it slow. Each plugin adds code, scripts, and database requests. Multiply that by 30 or 40 and you have a heavy site, full of background processes.

1.1. Types of plugins that typically slow down WordPress:

• Heavy page builders
• Social sharing plugins with live counters
• Statistics processed on frontend
• Sliders full of effects
• Old or outdated plugins

1.2. Audit your plugins

Go to Plugins > Installed and ask yourself: do I really need this?

Deactivate one by one and test speed.

Replace or eliminate. Less is more, ideally less than 15 active plugins on a simple site.

Keep only what's essential.

Expected result: up to 40% faster with just this cleanup.

2. Unoptimized Images

Images are often 70% of a page's weight.

If you upload directly from your phone, you're loading 3-5MB files and killing performance.

2.1. Resize before uploading

Go to iloveimg.com/resize-image and reduce image dimensions to the right size:

• Hero image: 1200×630px
• Content images: 800–1000px
• Thumbnails: 300×300px

2.2. Convert to WebP

Use cloudconvert.com/jpg-to-webp.

WebP format is up to 30% lighter than JPEG while maintaining great quality.

2.3. Upload the WebP version instead of JPG or PNG

• JPG → best for photos
• PNG → only for images with transparency
• WebP → use whenever you can

Quick tip: If you publish many images, install the ShortPixel or Smush plugin to optimize everything automatically in the background.

Expected result: 50-70% reduction in total page weight.

3. Missing Lazy Loading (Images and Videos)

Even with light images, how they load makes all the difference.

Lazy loading defers image loading until the user actually needs to see them.

It's simple and has a significant impact on loading speed.

3.1. Update WordPress

Since version 5.5, lazy loading is active by default. If your site is outdated, you're probably not taking advantage of this feature.

3.2. Activate the Lazy Load by WP Rocket plugin

It's free, lightweight, and works in seconds.

Just install and activate — no complicated setup needed.

It automatically applies lazy load to images, iframes, and videos.

3.3. For videos (YouTube or Vimeo)

Video embeds are heavy. Lazy Load by WP Rocket replaces the video with an image until the user clicks to watch.

That alone can cut megabytes from the initial load.

Expected result: 30% to 50% reduction in page loading time, especially on mobile.

4. Missing Cache

This is the game-changer.

Cache is what makes the difference between a site that breathes and one that chokes.

Without cache, WordPress has to generate everything from scratch with each visit, heavy and slow.

With cache, the server shows a saved version of the page. Much faster.

4.1. Install the WP Fastest Cache plugin

It's free, lightweight, and works very well with most hosting providers.

4.2. Activate the basic options:

• Cache enabled for desktop and mobile
• CSS and JS minification
• Gzip Compression
• Browser Caching

Save the changes and test your site again on PageSpeed Insights.

You'll notice the difference.

Expected result: loading time up to 80% faster.

Conclusion: What to Take Away

The 5 causes: plugins, images, loading, and cache are responsible for 90% of WordPress performance issues.

A fast site conveys trust, shows care, and makes your brand feel alive, not heavy.

At Hazel, we believe design is emotion, and speed is part of that.