Websites
Why is my website slow? How to test and fix it
You can test a site's speed for free with PageSpeed Insights, which reports three Google measurements called Core Web Vitals: how long the main content takes to appear (LCP, good under 2.5 seconds), how quickly the page responds to a tap (INP, good under 200 milliseconds) and how much the layout jumps while loading (CLS, good under 0.1). In 2025, only 48% of websites passed all three on mobile. The most common causes of a slow site are oversized images, scripts added by third-party services and heavy themes or plugins.
Contents
Key points
- Google considers a page good when its main content shows within 2.5 seconds, it responds to taps in under 200 ms and it doesn't jump around while loading.
- In 2025, 48% of websites passed all three tests on mobile and 56% on desktop, according to the Web Almanac.
- On mobile, WordPress sites passed in 45% of cases and Wix sites in 74%.
- A Deloitte study for Google found 8.4% more retail conversions when mobile pages loaded just a tenth of a second faster.
A slow website loses people before they read a word. Here's how to test yours for free, how to read the numbers and what usually slows a site down, in the order worth checking.
How to test your site's speed
The easiest tool is PageSpeed Insights, Google's free speed test. Enter your site's address and you get two things:
- Real-visitor data (top): how the site loaded for people who used it in Chrome over the last 28 days. It only appears if the site has enough traffic.
- A lab test (bottom): a simulated load on a mid-range phone, with a score from 0 to 100 and a list of issues.
Look at the mobile results first: most visitors to a local business come from phones, and that's where differences are felt most. If you use Search Console, its Core Web Vitals report shows the same measurements for every page on your site.
What LCP, INP and CLS mean
Google measures a page's experience with three numbers, called Core Web Vitals:
| Metric | What it measures | Good | Poor |
|---|---|---|---|
| LCP (Largest Contentful Paint) | How long the biggest element on screen takes to appear, usually the main photo or headline | Under 2.5 seconds | Over 4 seconds |
| INP (Interaction to Next Paint) | How quickly the page responds when you tap a button or open the menu | Under 200 ms | Over 500 ms |
| CLS (Cumulative Layout Shift) | How much things jump around while loading, like a button moving as an image appears | Under 0.1 | Over 0.25 |
A page passes when all three are good for at least 75% of visits. INP replaced the older FID metric in March 2024, so older reports may show different numbers.
How fast websites are in general
The Web Almanac, HTTP Archive's yearly report on how the web is built, found in 2025 that:
- 48% of websites pass all three tests on mobile and 56% on desktop;
- on mobile, 62% have a good LCP, 77% a good INP and 81% a good CLS, so loading the main content is the most common problem;
- on 76% of mobile pages, the largest element on screen is an image.
The platform you're on makes a big difference. On mobile, WordPress sites passed all three tests in 45% of cases, while Wix sites reached 74%, up from 55% a year earlier.
Why speed matters
For customers. In a study Deloitte ran for Google across 37 brands in Europe and the US, a mobile speed improvement of just 0.1 seconds came with 8.4% more conversions for retail sites and 10.1% more for travel sites. It's a correlation, not a controlled experiment, but the direction is clear: fractions of a second matter more than they seem.
For Google. Google says it highly recommends good Core Web Vitals for success in Search and that they align with what its ranking systems seek to reward. They're not the main factor, though: a page that answers the search better beats a faster but thinner one. Speed helps most when competing pages are equally good.
What slows a website down
| Cause | How it shows in PageSpeed | Fix |
|---|---|---|
| Oversized images | Suggestions about image size and format | Images at display size, in WebP or AVIF |
| Main photo loading late | High LCP, the image appears last | Load the main photo first, with no fade-in effects |
| Third-party scripts | Lots of code loaded from other domains | Remove what you don't use: chat widgets, old pixels, embeds |
| Heavy theme or plugins | Lots of unused JavaScript | Fewer plugins, a lighter theme or a site built in code |
| Slow server | Long time to first byte (TTFB) | Caching, better hosting or pages generated ahead of time |
| Too many fonts | Text appearing late or changing shape | Two typefaces, only the weights you use |
| Jumping elements | High CLS | Fixed dimensions for images, ads and banners |
| Slider or video at the top | High LCP on mobile | One well-chosen image |
On small sites, most problems come from the first three rows. A slider with five 3 MB photos, or a chat widget that loads half a megabyte of code, is felt on any phone.
What you can fix without a developer
- Compress images before uploading. Squoosh (squoosh.app) is free and turns a 4 MB photo into a 200 KB one with no visible difference on screen.
- Remove plugins and scripts you no longer use: an ad pixel from an old campaign, a replaced form, a chat nobody answers.
- Swap the slider for one image and a clear headline.
- Retest after each change with PageSpeed to see what made a difference.
If the site is still slow after all that, the problem is usually how it's built: a theme that loads everything on every page, or a visual builder that adds a lot of code. That's when a redesign that keeps your page addresses is worth considering.
The sites we build use Next.js, with pages generated ahead of time as ready HTML, so they open quickly even on an average phone. The details are on our web design page.
Questions
How do I test my website's speed for free?
Go to pagespeed.web.dev, enter your site's address and look at the mobile results. The top section shows what real visitors experienced over the last 28 days, if the site has enough traffic; the bottom is a lab test with suggestions.
What's a good PageSpeed score?
Above 90 is very good, but the score comes from a lab test. What matters more is whether the three Core Web Vitals from real visitors are green: LCP under 2.5 seconds, INP under 200 ms and CLS under 0.1.
Does site speed affect Google rankings?
Yes, but it isn't the biggest factor. Google recommends good Core Web Vitals and says they align with what its ranking systems reward, but a slower page that answers the search better can still rank first.
Why is my website slow on mobile but fast on desktop?
Phones have slower processors and often slower connections, and mobile tests simulate exactly that. Large images and heavy scripts hurt far more on an average phone than on a laptop.
Will better hosting make my site faster?
Only if the server is slow to respond, which PageSpeed shows as a long time to first byte. If the problem is images or scripts, more expensive hosting changes almost nothing.
Sources
- Understanding Core Web Vitals and Google search results, Google Search Central
- Web Almanac 2025: Performance, HTTP Archive
- Web Almanac 2025: CMS, HTTP Archive
- Milliseconds make millions, web.dev (Google)
- PageSpeed Insights, Google