A preloader is a loading screen image or gif that displays before the main content of a page is fully loaded.
Step 1 : From your Shopify admin, go to Online Store > Themes.
Step 2 : Find the theme that you want to Edit and Click Customize.
Step 3 : Click Theme Settings > Preloader.
Enable the toggle for preloader option.
In the preloader options, you can add an image or gif to display as a preloader in your store by selecting Select Image.
Finally click save.
