Before we begin:
- The following article demonstrates the solution that is applicable for classic SharePoint sites only. Please note that modern SharePoint sites do not have an option to add a preloader.
- Supported platforms: Office 365 (SharePoint Online), SharePoint 2019, SharePoint 2016, SharePoint 2013.
You followed the steps of How to Show only the Logo Image (or a Custom Spinner) in the ShortPoint Preloader solution to set the custom preloader, and now it appears that the preloader slows down loading the page.
The preloader itself does not affect the page performance and cannot influence the page loading time.
The issue here might be with the user experience, when using custom images or GIFs.
The browser is reading the code, and loads the standard preloader first (a standard circle spinner, that is hidden now as was advised in the article - step 3), and then reads the information from the link to the custom preloader. It takes some time, and it looks like the page became slower, but it is only the loading time of the preloader, not the page performance.
Step 2: Update the Logo URL in the Theme Builder
Step 3: Add the updated preloader to your site
Here is how the updated preloader looks now: