Blocs has a built in feature that is designed to help web pages load faster. This feature is called Lazy Load and is enabled on all new projects by default.
How Does Lazy Load Work
When a browser is loading a web page it has to load every single item on the page regardless of whether it’s initially on screen or not. If you have a lot of videos or high resolution images on your site, this can cause the page to load very slowly. Some of the content that causes this slowing down can sometimes be half way down the page or even in the footer of the page. This is where Lazy Loading can increase page load speeds dramatically.
Lazy Loading tells the browser to only load the parts of your web page that are on screen when you first load the page, these items are referred to as being above the fold. As you scroll down the page, the browser will then quickly load the items that will soon be visible on screen. Using Lazy Loading not only speeds up your page loads, it also helps decrease the bandwidth usage for your site on your server.
Disable Lazy Load
You can disable Lazy Load for a project via the advanced export options. You can access these options using File > Export > Export Project from the apps main menu or using the keyboard shortcut ⇧+⌘+E.