A site that loads quickly on launch day can be slow a year later without anyone noticing. Speed is the result of small decisions made over time, not a single setting.
Images are usually the reason
The most common cause of a slow page is a large photo dropped straight into the page. Before you upload anything, resize it to roughly the width it will be shown at and export it as a compressed file. A full width photo on a phone does not need to be thousands of pixels across.
If you take product photos on a phone, keep the originals somewhere safe and upload the resized copies.
Be careful with add-ons
Every plugin, widget and script you add has to load before the page can be read. Each one costs a little time, and the costs add up. Before installing anything, ask whether the page actually needs it and whether a simpler approach would do the same job.
Watch what loads in the background
Third party embeds, chat widgets and font sets all add requests. Keep the ones you use and remove the ones you do not. If a script does not clearly help a visitor, it is probably not worth its cost.
Check it yourself, regularly
Open your site on a phone using mobile data, not just on your office connection. Time how long the main content takes to appear. If it takes more than a few seconds, look at the page weight first, since images are the usual cause.
Do this once a month. It takes a minute and it catches problems early.
Keep the site updated
Update the platform your site runs on and anything installed on it. Updates often include fixes that keep the site working and quick. Back the site up before you update, so you can go back if something breaks.
When to ask for help
If a page has become slow and you cannot see an obvious cause, send us the address. We can look at what the page is loading and tell you where the time is going.