In more detail
What slows a site down
People searching on their phones are often on the move, on mobile data, with little patience. If your page is still loading while a competitor's is ready, many will simply go back and tap the next result. Speed is not a technical nicety. It decides whether visitors ever see your work.
Images are the most common cause of a slow site. Photos straight from a camera or phone are far larger than a web page needs. Resizing them to the size they are actually shown, compressing them and using modern formats can make a big difference without any visible loss of quality. Images further down the page can also be set to load only when someone scrolls to them.
Hosting is the foundation. Cheap shared hosting can be slow to respond, especially when other sites on the same server are busy. Good hosting serves pages quickly and close to your visitors, often using a content delivery network that keeps copies of your site in many locations.
Clutter is the third culprit. Over time, websites collect plugins, tracking scripts, chat widgets, sliders, pop ups and fonts. Each one adds weight and work for the phone to do before the page is usable. Ask of each item whether it earns its place. Removing a few things nobody uses can speed up every page.
Website builders and heavy themes can add their own overhead, loading code for features you never use. That is one reason two sites that look similar can perform very differently.
The test from the video is the most honest one. Open your site on your phone, on mobile data rather than office wifi, and count how long it takes before you can actually read and tap things. Then do the same for a competitor. Free tools such as Google PageSpeed Insights can tell you more, but your own thumb and your own patience are a good start.
