Performance By Lui Nobrega · Jun 3, 2026 · Updated Oct 26, 2026 · 5 min read

Why Page Speed Is Costing You Customers

A slow website is not just annoying. It costs you money. People decide whether to stay before your page has even finished loading, and they never tell you why they left. Here is how to test your own site, what the numbers mean, and what usually fixes them.

What counts as fast

Google measures real visits with three numbers called Core Web Vitals. Each one has a "good" line. Google checks the visit at the 75th percentile, so most of your visitors, not just the lucky ones, should get a good experience. Interaction to Next Paint replaced an older measure, First Input Delay, in March 2024, so older articles may still mention FID.

  1. Largest Contentful Paint (LCP) is how long until the main content, often the big photo or headline, shows up. Good is 2.5 seconds or less. Poor is over 4 seconds.
  2. Interaction to Next Paint (INP) is how fast the page reacts when someone taps or clicks. Good is 200 milliseconds or less. Poor is over 500 milliseconds.
  3. Cumulative Layout Shift (CLS) is how much the page jumps around while it loads. Good is 0.1 or less. Poor is over 0.25.

Helpful links

Test yours in five minutes

You do not need to be technical for this. Test your home page first, then your most important service page.

  1. Open PageSpeed Insights, paste your web address and select Analyze. See: PageSpeed Insights (opens in a new tab)
  2. PageSpeed Insights tests both a phone and a desktop visit. Check the Mobile tab and the Desktop tab.
  3. Look at the top section first. It shows real visits from the past 28 days and says whether the page passes the Core Web Vitals assessment. A newer or quieter site may not have enough visits yet, and then this section is empty. See: About PageSpeed Insights (opens in a new tab)
  4. Below it is a lab test with a score from 0 to 100. Google counts 90 or above as good, 50 to 89 as needs improvement, and below 50 as poor. The lab test is a single simulated visit, so it can differ from real visits.
  5. Scroll down to the suggestions. They point at the exact images and files that slow the page down. Note the top three.
  6. If your site is in Google Search Console, open the Core Web Vitals report. It groups a sample of your pages into Good, Need improvement and Poor. See: Core Web Vitals report (opens in a new tab)

What makes a site slow

Usually it is huge photos that nobody ever shrank. Page builders and plugins add code you never use. So do tracking tools that someone added years ago and forgot. One giant photo at the top of the page can undo everything else you did right.

Fix the photos first

Start with photos. They are the part you can most easily fix yourself.

  1. Make each photo only as big as it needs to be. A photo shown 800 pixels wide may need about 1,600 pixels for sharp phone screens, but not 4,000. See: Properly size images (opens in a new tab)
  2. Save photos as WebP or AVIF where your site supports it. Google's web.dev says both generally compress better than JPEG and PNG. See: Choose the right image format (opens in a new tab)
  3. Shrink each photo before you upload it. Squoosh, an image tool from Google Chrome Labs, runs in your browser. Your photos never leave your device. See: Squoosh (opens in a new tab)
  4. Ask your developer to lazy-load photos further down the page. The big photo at the top should load right away, not lazily. See: Browser-level image lazy loading for the web (opens in a new tab)

Then cut the extra code

Every chat widget, tracking tag and plugin adds work for the visitor's phone. Keep the ones that earn their place.

  1. List every outside script on your site: chat widgets, tracking tags, social feeds, pop-ups. Google's first piece of advice for a slow outside script: remove it if it does not add clear value. If you need it, ask your developer to make it load more efficiently. See: Efficiently load third-party JavaScript (opens in a new tab)
  2. On WordPress, deactivate and then delete plugins you no longer use, and keep the rest up to date. WordPress says updates help both security and performance. See: Manage Plugins (opens in a new tab)
  3. Run PageSpeed Insights again after each change, so you know which fix helped.

Google is watching too

Google recommends good Core Web Vitals for success in Search, and says they line up with what its ranking systems reward. Speed is not the only thing that counts. Google says it still shows the most relevant page first, even if it is slow. But when several local businesses offer the same thing, a better page experience can help you.

Helpful links

Common questions

What is a good PageSpeed Insights score?

Google counts a score of 90 or above as good, 50 to 89 as needs improvement, and below 50 as poor. The Core Web Vitals from real visits matter more than the score, because they show what your actual visitors experienced.

Why does my score change every time I test?

The score comes from one simulated visit, and network conditions vary from run to run. The real-visit data covers the past 28 days, so it moves more slowly. Test a few times and look at the trend.

Does page speed affect my Google ranking?

It can help, but it is not the whole story. Google recommends good Core Web Vitals and says page experience can contribute to success in Search, while relevant content still comes first.

Sources and further reading

The takeaway

Test your site with PageSpeed Insights, aim for the good line on all three Core Web Vitals, shrink your photos and cut the scripts you do not need. Then test again.

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