Your laptop is not the device the site is being judged on
The office tests on new hardware over office internet with everything already cached. The customer has none of those three things, and each one is worth more than the others combined.
Because you are testing a cached site on a fast device over a fast connection, and your customer is loading it cold on a mid-range phone over mobile data. The gap between those two conditions is large enough that a page can feel instant to the team and take several seconds for the people buying from it.
Three differences, and they multiply
The device does the work. Parsing and running scripts is processor work, and a mid-range phone can take several times longer than a laptop on exactly the same page. Nothing about the page changed, only what is executing it.
The connection adds latency to every request, and mobile latency is far higher than office wifi even when the reported speed looks similar. Then there is the cache: your team has visited the site all week, so the fonts, scripts and images are already on the machine and never fetched.
- A mid-range phone runs the same script several times slower
- Mobile latency is paid on every separate request
- Your team's browser already holds the files a customer must download
- Ad blockers and extensions in the office remove weight customers still receive
What usually turns out to be the cause
It is rarely the server and rarely the images, because both of those get attention early. It is usually script weight: analytics, a chat widget, a heat map recorder, a consent banner, a personalisation tool, each added by a different person for a different reason.
Each of those runs on the customer's processor. On a laptop the total is invisible. On a phone it is the difference between a page that responds to a tap and a page that appears to have frozen.
How to see what they see
Test the way the customer arrives: a phone rather than a laptop, mobile data rather than office wifi, and a private window so nothing is cached. Do it on the page that sells, not on the home page, because the home page is usually the only one anybody optimised.
Field data from real visitors is better still, because it includes devices nobody in the office owns. It is available for most sites and it settles arguments that opinion cannot.
The fix that is almost always available
Count every script the page loads and name the person who wants it. In most cases several belong to campaigns that ended, tools nobody logs into, and features that were trialled and never removed.
Deleting those is faster, cheaper and safer than any rebuild, and it is the only intervention where the benefit is certain before the work starts.
What to take from this
- 01Device, connection and cache all differ between the office and the customer
- 02Script weight is usually the cause, and it accumulates from many small decisions
- 03Test on a phone, on mobile data, in a private window, on the page that sells
- 04Removing unused scripts beats rebuilding, every time
Ask the question directly
- Our hosting is fast. Is that not enough?
- Server time is one part of the total and often a small one. If most of the delay happens after the page arrives, a faster server changes nothing a visitor can perceive.
- Do we have to remove analytics and chat?
- Not necessarily. Load them after the page is usable rather than before it, and remove the ones nobody has opened in six months, which is usually most of the list.
- Which page should we measure?
- The one that produces revenue: a product page, a service page, whatever the ads point at. The home page is frequently the least representative page on the site.
Related answers
Web development
New builds, rescues and re-platforms, measured against what the site earns rather than against how it looks. The brand system that carries it is built in the same engagement.
SEO management
One monthly programme: technical fixes, content architecture and internal links, aimed at the queries that end in a sale rather than the ones that end in a visit.
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