SEO · 11 min read · Updated:
How to measure website speed: reading Core Web Vitals and PageSpeed the right way
A speed test gives you one score, but the real information sits underneath it. We explain what each measure tells you and what to fix first, step by step.
In short
- Website speed is best measured with Google's free PageSpeed Insights tool, which shows both a lab test (Lighthouse) and real visitor data.
- Core Web Vitals are three measures: LCP, how fast the main content appears (good under 2.5 s); INP, how fast the page responds to a tap (good under 200 ms); and CLS, how much the layout shifts while loading (good under 0.1).
- Real visitor data covers the last 28 days at the 75th percentile; a single lab score can move by a few points between runs.
- On small business sites the most common cause of slowness is oversized images, and the phone score should be checked before the desktop score.
- In Heyşirket, the SEO › Speed screen on the Professional plan measures the home page daily and shows score history and the improvements with the biggest gain.
A customer opens your site on their phone, the page stays white for three or four seconds, and they hit the back button. You never see this happen; you just wonder why so few enquiries come through the form. Measuring website speed turns that invisible loss into a number.
The good news: measuring speed needs no technical knowledge or paid tools. Google's own tool is free and tells you both a score and what to do about it. The hard part is reading the result correctly.
In this article we explain how speed is measured, what Core Web Vitals are, how a lab score differs from real visitor data, and which fix to make first.
- Measure — Phone first
- Read — LCP, INP, CLS
- Prioritise — Biggest gain
- Fix — Usually images
- Measure again — Watch for a few days
Part 1 · Why Why does website speed matter?
Speed has an effect in two places. The first is the visitor: a slow page demands patience, and people on phones are impatient. The second is the search engine: when Google evaluates page experience, it also uses Core Web Vitals.
It's important not to overstate this. Speed alone won't take you to the top; content and how well you answer the search always come first. But between two sites with similar content, the fast page that doesn't jump around stands out, and visitors stay longer. We cover the bigger SEO picture in what is SEO.
Part 2 · Measuring How do you measure website speed?
Google's website speed tool is PageSpeed Insights. You type your page's address, and a few seconds later you get separate results for phone and desktop. The same engine is also built into Chrome's developer tools under the name Lighthouse.
Your first test with PageSpeed Insights
Pick the right page
Measure your home page first, then your most visited inner page. A service or product page can be slower than the home page.
Start with the mobile tab
The phone test uses a slower connection and processor. Since most visitors come from phones, this is the real exam.
Look at the real-user box at the top
If your site has enough traffic, the Core Web Vitals result from real visitors appears at the top. If not, only the lab test is shown.
Note the score, read the suggestions
Write down the performance score and the suggestions below it. After a fix, measure the same page on the same device again.
Part 3 · Three measures What are Core Web Vitals?
Core Web Vitals are the three measures Google chose to capture how a page feels to the user. One covers loading speed, one covers responsiveness and one covers visual stability. Since 2024 the responsiveness measure has been INP; the FID you see in older sources is no longer used.
| Measure | What it tells you | Good | Needs improvement | Poor |
|---|---|---|---|---|
| LCP (Largest Contentful Paint) | Time for the largest element on the page, usually the main image or heading, to appear | 2.5 s or less | 2.5 – 4 s | Over 4 s |
| INP (Interaction to Next Paint) | Time for the page to respond after a tap or click | 200 ms or less | 200 – 500 ms | Over 500 ms |
| CLS (Cumulative Layout Shift) | How much content moves while loading | 0.1 or less | 0.1 – 0.25 | Over 0.25 |
Picture an example. A dental clinic's home page has a large photo of the clinic. If the photo takes 4 seconds to appear, LCP is poor. If a late-loading announcement bar at the top pushes the Book an appointment button down just as the visitor is about to tap it, CLS suffers. If they tap the menu and wait half a second, the problem is INP.
You'll also see other measures on the screen: first contentful paint (FCP), total blocking time (TBT), speed index and server response time (TTFB). These aren't Core Web Vitals, but they show where a problem starts. For example, if server response is slow, shrinking an image won't be enough on its own.
Part 4 · Two sources Why do the lab score and real-user data differ?
PageSpeed reports from two different sources, and most confusion starts here. The lab test (Lighthouse) loads the page right now, assuming a particular device and connection. Real-user data is the experience of your actual Chrome visitors over the last 28 days.
| Lab test | Real-user data | |
|---|---|---|
| When? | The moment you run it | Last 28 days |
| What does it show? | A 0-100 score and suggestions | Good / needs improvement / poor for LCP, INP, CLS |
| How is it calculated? | A single page load | 75th percentile of visits |
| Available for every site? | Yes | Only for sites with enough traffic |
| Reaction to changes | Immediate | Gradually, over weeks |
The 75th percentile means three quarters of visits are at this value or better. So a few fast visits don't rescue the average; visitors on slow phones count too. Google's page experience assessment is based on real-user data.
Part 5 · Fixing Website speed optimisation: what should you fix first?
PageSpeed's list of suggestions can look long. You don't have to do them all. The first two or three items, which the tool sorts by estimated gain, usually deliver most of the difference. On small business sites the same causes come up again and again.
| Symptom | Likely cause | First fix |
|---|---|---|
| High LCP | A large photo or sliding image gallery on the home page | Shrink the photo, use a single image above the fold |
| High LCP, slow server response | Hosting or a chain of redirects | Remove unnecessary redirects, check the domain setup |
| High CLS | Images without dimensions, a late bar or a pop-up | Delay or remove the pop-up, reserve fixed space |
| High INP | Heavy custom code, lots of third-party tracking tags | Remove tags and add-ons you don't use |
| Low score despite little content | Embedded videos and maps | Move video and map further down the page |
A speed check that starts with images
- I resize photos below 2000 pixels wide before uploading.
- There's a single main image above the fold, no sliding gallery.
- Every image has a short alt text (not for speed, but for accessibility and search).
- The home page pop-up doesn't appear in the first seconds.
- I removed custom code and tracking tags I don't use.
- After the change I measured the phone score again and noted it.
Part 6 · Panel Where is the speed report in Heyşirket?
In Heyşirket the website is a module of your company panel, and speed measurement lives there too. The SEO › Speed screen on the Professional plan runs PageSpeed for you and keeps the results with their history, so you don't have to open the tool and type the address every time.
- Device choice: Phone and Desktop are measured separately at the top. Look at the phone first.
- Lighthouse scores: rings for Speed, SEO, Accessibility and Best practices; 90 and above counts as good.
- Core Web Vitals: cards for LCP, INP and CLS. With enough data, the last 28 days of real visitors are shown; otherwise the screen says it's a lab measurement.
- Speed score history: the home page is measured once a day; phone and desktop lines sit side by side. This is where you see the effect of a change.
- Recommended improvements: a list sorted by Google's estimated gain.
- Key pages: your three most clicked inner pages are measured on phone once a week.
Images are easy too. Large images you upload to the Media library are resized automatically, and for older images there's a Generate sizes for existing images button. Step-by-step guide in the panel: Help › Speed report and Core Web Vitals.
On the free Starter plan the speed screen appears locked; on that plan you can measure your site yourself in PageSpeed Insights using the steps above. If Search Console is connected, real-user data shows up there too; the steps are in connecting Search Console and Google Analytics. For an overview of the SEO tools that include the speed report, see the SEO tools page.
Part 7 · Routine How often should you measure speed?
Speed isn't something you fix once and forget. A new campaign image, an added video or a new tracking code can drop the score in a day. That's why measurement needs to be part of a routine.
- After every big change: home page design, a new section, a new pop-up or a theme change.
- Once a month: a general look at the phone score and Core Web Vitals, and at your key pages.
- When traffic drops: if search traffic falls suddenly, check the speed history too; it's rarely the only reason, but it's one of the first to rule out.
If you also want to track your site's overall SEO health alongside speed, the panel's SEO centre shows your score and tasks together. For the first setup, see first steps with the SEO centre.
How do you measure website speed?
Type the page's address into Google's free PageSpeed Insights tool. It gives a separate performance score for phone and desktop, the Core Web Vitals result and suggestions for improvement. Check the phone result first.
What are Core Web Vitals?
Core Web Vitals are the three measures Google uses to assess page experience: LCP is how long the main content takes to appear, INP is how quickly the page responds to a tap, and CLS is how much the page shifts while loading. The good thresholds are 2.5 seconds for LCP, 200 milliseconds for INP and 0.1 for CLS.
Why does my PageSpeed score change every time?
The lab test is based on a single page load, and server load, network conditions and outside resources affect it. A swing of a few points is normal. When deciding, look at the average of several runs and at real-user data.
Does my PageSpeed score have to be 100?
No. The goal is for the Core Web Vitals measures to be in the good range. A phone score of 90 or above is good; chasing 100 isn't worth giving up content or usability.
Why can't I see real-user data?
Real-user data is collected from Chrome visitors and is shown for sites that reach enough visits. New or low-traffic sites only show the lab test; in that case, working from the lab result is enough.
Which Heyşirket plan includes the speed report?
The SEO › Speed screen is available on the Professional and Premium plans. The home page is measured once a day for phone and desktop, and score history and suggestions are kept. On the Starter plan you can measure your site yourself in PageSpeed Insights.
See your site's speed in the panel Open your phone score, Core Web Vitals result and the improvements with the biggest gain on one screen. Open the speed report
If you don't have a site yet, start for free; when you need SEO tools like the speed report, you upgrade your plan from the panel.
Author: Heyşirket Editorial Team