A site that feels quick on office fibre can be unusable in a garage downtown or a truck stopped on 35E.
Where the page really gets opened
Stopped in traffic on the LBJ. In a parking garage where the signal dies two levels down. Standing in a driveway holding the phone up at a roof.
That is where the site is judged, out on a downtown parking garage, and it is nothing like the desk it was approved at. Eight seconds there hands the job to whoever managed two.
What a builder quietly ships with it
A builder has to handle any arrangement a customer might dream up, so it loads the whole toolkit before knowing what you used. A few service pages end up towing a layout engine, a motion library, and an icon set nobody opened.
Publishing trims none of it away. It goes out to every visitor, on every page, over a downtown parking garage included, from here on.
Photographs straight off the handset
One shot off a modern phone is four to eight megabytes. Ten in a gallery asks a stranger on cellular to pull down about fifty.
Run through a resizer those ten total roughly four hundred kilobytes and look no different on a screen. Nothing else you can do to a small site helps this much.
Everything that got bolted on
The chat tab, the spinning testimonials, the coupon overlay, the embedded scheduler, the tracking tags, the consent notice. Each rings a different company, and the page stays half-built until all of them reply.
On a weak connection they time out in sequence while the visitor stares at grey panels. Very few of them return more work than the wait costs.
Typefaces that hide your own words
Four font files usually means the sentences stay invisible until the last one lands, and out on a downtown parking garage that is a long wait. From the visitor's side that is a white screen, indistinguishable from a site that has crashed.
Two weights, hosted yourself, words showing in a fallback from the first frame. Nobody in Texas has ever hired a roofer for the lettering.
Test it the way it gets used
Kill the wifi, sit in a garage downtown, and load your own homepage. That tells you more than any score a tool will hand you.
Three seconds should be enough to read the opening line and find the number. If it is not, something has to come off the page.