Why Is My Website So Slow? 9 Causes and How to Fix Them

Short answer: Most slow websites are slowed down by the same few things: oversized images, too many plugins or apps, a heavy theme or page builder, too many third-party scripts, and cheap or overloaded hosting. Fix images and plugins first; they’re usually the quickest wins.

Speed matters for two reasons. Visitors leave pages that take too long to appear, and Google uses page experience signals, including Core Web Vitals, when ranking pages. Below are the nine most common causes, how to spot each one, and how to fix it.

First, measure your speed

Open PageSpeed Insights, enter your page and check the Mobile tab. Look at the three Core Web Vitals, which Google defines like this:

Metric	What it measures	Good	Poor
LCP (Largest Contentful Paint)	How fast the main content appears	2.5 s or less	Over 4 s
INP (Interaction to Next Paint)	How fast the page responds to taps and clicks	200 ms or less	Over 500 ms
CLS (Cumulative Layout Shift)	How much the layout jumps while loading	0.1 or less	Over 0.25

Google judges each metric at the 75th percentile of real visits: if at least 75% of visits are “good”, the page passes. Test your home page and your most important service or product page.

The 9 most common causes

1. Images that are too big

A photo straight from a phone can be 3–5 MB. On a mobile connection, that alone can take seconds. Fix: resize images to the size they’re shown at, convert them to WebP or AVIF, and lazy-load images below the first screen. Don’t lazy-load the main hero image; that delays LCP.

2. Too many plugins or apps

Every WordPress plugin or Shopify app can add its own scripts and styles to every page, even pages that don’t use it. Fix: list what’s installed, remove what you don’t use, and replace several small plugins with one, or a few lines of custom code.

3. A heavy theme or page builder

Multi-purpose themes and page builders load code for features you never use and wrap content in many nested layers. Fix: switch heavy pages to the WordPress block editor or a lightweight theme, or turn off builder features you don’t need.

4. Too many third-party scripts

Chat widgets, multiple analytics tools, ad pixels, embedded social feeds and pop-up tools each load code from another server. Fix: keep only the tracking you actually look at, load chat and pop-ups after the page has loaded, and replace embedded feeds with a link.

5. Cheap or overloaded hosting

If the server is slow to respond, everything else waits. Very cheap shared hosting often puts hundreds of sites on one server. Fix: check “server response time” in PageSpeed Insights. If it’s consistently slow, move to better hosting with LiteSpeed or a similar fast server and server-side caching.

6. No caching

Without caching, WordPress rebuilds every page from the database on every visit. Fix: enable page caching (for example LiteSpeed Cache or WP Rocket on WordPress) and browser caching. Add object caching (Redis) for stores and busy sites.

7. Fonts and render-blocking files

Large font files and CSS or JavaScript in the page head stop the browser from showing anything until they load. Fix: use no more than two font families, host them yourself, and defer non-critical JavaScript.

8. A bloated database

Old post revisions, expired data and leftovers from deleted plugins slow down WordPress and WooCommerce over time. Fix: clean the database with a trusted tool after taking a backup, and limit post revisions.

9. No CDN

If your visitors are far from your server, every file travels a long way. Fix: put the site behind a CDN such as Cloudflare. Its free plan is enough for many small business sites.

What to fix first

1. Compress and resize images.
2. Remove unused plugins, apps and scripts.
3. Turn on caching.
4. Check hosting response time and upgrade if needed.
5. Then deal with theme, fonts and code.

After each change, test again in PageSpeed Insights and check that forms, checkout and tracking still work.

FAQ

Sources: web.dev – How the Core Web Vitals thresholds were defined