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Why your website has to load fast on a phone, and how to check

Most of your customers are on a phone, and a slow site loses them fast. Here is how to test yours in two minutes, and what the numbers mean.

Zeno BelskyBy Zeno Belsky··5 min read

Most of the people looking at your website are doing it on a phone, standing in a supermarket queue or sitting in a car in Newmarket, on mobile data that is nowhere near as quick as the office wifi you built the thing on. If your site takes more than about three seconds to show up, research says roughly half of them give up and go back to Google. The good news is you can check exactly how yours performs, on a real phone connection, in about two minutes and for nothing, using Google's own free tool. Here is how, and what the result actually means.

Why the phone is the only screen that counts now

In New Zealand this is not a close call. More than nine in ten people who use the internet here do it on a phone, and for a local business, a plumber, a cafe, a physio, the share arriving on your site from a mobile is usually higher again, because people reach for you when they are out and about and need something sorted. The desktop visit is the exception now, not the rule.

That matters because your phone and your customer's phone are living completely different lives. Yours is on fast home or office broadband, and it has already saved half your site from the last time you looked at it. Theirs is cold, on three bars of 4G, loading every image from scratch. The site that feels instant to you can be a slow, stuttering mess for the person you actually want to reach. You never see that version, so you assume it is fine. That is the trap.

How do I actually check my website speed?

Open pagespeed.web.dev in any browser. That is Google PageSpeed Insights, it is free, and it does not ask you to sign up or hand over a thing. Paste in your full web address, the whole lot with the https at the front, and hit Analyse. Wait fifteen or twenty seconds while it does the work.

When the results load, look at the top and make sure you are on the Mobile tab, not Desktop. This is the bit people miss. PageSpeed deliberately tests your site on a throttled, slow-4G connection, the kind your customer in the car park is genuinely on, so the mobile score is meant to look worse than the desktop one. Do not panic at a lower number there. That is the honest one, and it is the one that decides whether you win the enquiry.

WHAT GOOD LOOKS LIKE ON A PHONEMain content shows. under 2.5 seconds (LCP)Taps respond fast. under 200 milliseconds (INP)Nothing jumps around. score under 0.1 (CLS)All three green. that is the whole target
The three Core Web Vitals and the numbers to aim for on mobile.

What do the numbers actually mean?

You will get a score out of a hundred and, more usefully, three measurements Google calls Core Web Vitals. You do not need the engineering behind them, just what each one is asking:

  • LCP, largest contentful paint. How long until the main thing on the page, usually your big header image or headline, has actually appeared. Aim for under 2.5 seconds.
  • INP, interaction to next paint. How quickly the page reacts when someone taps a button or opens the menu. Under 200 milliseconds is the mark.
  • CLS, cumulative layout shift. Whether things jump around while the page loads, so you go to tap one thing and something else slides under your thumb at the last second. You want that close to zero, under 0.1.

Green is good, orange is borderline, red needs work. The only question that matters is whether the three sit in the green. If they do not, the report tells you which one is dragging, and that is your starting point.

Mine is slow. Now what?

First, do not reach for the miracle plugin that swears it will fix the lot. Speed is what you get when a site is built light from the start, not a switch you flip at the end. The usual culprits are dull and completely fixable: huge images straight off a phone, a pile of plugins all loading at once, bargain hosting, a heavy drag-and-drop theme. We wrote out the full list and the real fixes in why your website is slow, so start there.

If you would rather not go poking around under the bonnet yourself, flick us your web address. We will run it properly, tell you straight what is dragging it down, and whether it is a quick tune-up or something deeper. No jargon, no upsell. A sharp small-business site from us runs about NZD 4,000 to 5,000, against the 6,000 to 10,000 and up you will see around town for the same job. Sites that go boom, not bust.

Quick answers

Is a low mobile score on PageSpeed Insights bad?

Not on its own. Google tests the mobile version on a deliberately slow 4G connection, so the mobile number is always lower than desktop. What matters is whether your three Core Web Vitals, LCP, INP and CLS, sit in the green, not the exact score out of a hundred.

How fast should a website load on a phone?

Aim to have the main content visible in under 2.5 seconds on a mobile connection. Past about three seconds, research puts the share of mobile visitors who give up and leave at over half, so every extra second is lost enquiries.

Does website speed affect my Google ranking?

Yes. Page speed and the Core Web Vitals feed into how Google ranks pages, and the mobile version is the one it judges you on. A slow site is harder to find, and then it loses the people who do find it.

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