Nobody makes a site slow deliberately. It happens by accumulation, a little at a time, until someone notices it takes four seconds to load and cannot say when that started.
Images uploaded at camera resolution
The most common cause by a distance. Someone uploads a 4MB photograph straight from a phone, the page scales it down in the browser, and it looks fine — while every visitor downloads all four megabytes. Ten of those and the page is unusable on mobile data.
The fix is to resize and convert on upload rather than trusting whoever is adding content to remember. Modern formats cut the same image by half again.
Third-party scripts, one at a time
Analytics, then a chat widget, then a heat map, then a pixel, then a booking embed. Each is individually small and each was approved by someone reasonable. Together they can outweigh the site itself, and they run on the visitor's device, competing with your own content.
Audit them annually and ask what each is actually used for. Most sites are carrying at least one script nobody has looked at in a year.
Plugin and dependency creep
Every plugin is code you did not write, loading on pages that may not need it. Over a few years a site can be carrying features that were trialled once and never removed.
The database quietly growing
A table that was fast with five hundred rows behaves differently at half a million, especially without the right indexes. Order history, logs, form submissions, revisions — all grow silently and none announce that a query has become the bottleneck.
Caching that stopped working
Caching layers get disabled during debugging and not re-enabled, or a change invalidates everything on every request. This one is invisible until measured, because the site is correct — just doing work it should not repeat.
How to find out which it is
Measure with field data first — what real visitors experience — then use lab tools to identify causes. Guessing produces optimisation of things that were never the problem.
How we approach it
Speed work is engineering, which is why our SEO and development sit together. Related reading: does website speed affect rankings.
Ask us to look at your site if it feels slower than it used to.