Source: https://yatesdesign.com.au/divi-tutorial-reveal-footer-scroll/

/*Divi fixed position footer by yatesdesign.com.au*/
 
#main-content {
 margin-bottom: 350px; /*This may to be adjusted depending on the content of your footer*/
}
 
#main-footer {
 position: fixed;
 z-index: -1;
 height: 350px; /*This may to be adjusted depending on the content of your footer*/
 width: 100%;
 bottom: 0;
}
 
#footer-bottom {
 position: fixed;
 width: 100%;
 bottom: 0;
 padding: 10px 0;
}
 
#footer-info, #footer-info a {
 padding: 0;
}
 
#main-footer .container {
 height: 100%;
}
 
#footer-widgets {
 position: absolute;
 bottom: 51px; /*This may to be adjusted depending on the content of your footer*/
}
 
/*Edit this section for tablet-sized screens*/
@media only screen and ( max-width: 980px ) {
  
 #main-content {
 margin-bottom: 450px;
 }
 
#main-footer {
 height: 450px;
 }
 
#footer-widgets {
 bottom: 83px;
 }
 
}
 
/*Edit this section for phone-sized screens*/
@media only screen and ( max-width: 767px ) {
 
#main-content {
 margin-bottom: 650px;
 }
 
#main-footer {
 height: 650px;
 }
 
#footer-widgets {
 bottom: 83px;
 padding: 5% 0;
 }
 
#footer-widgets .footer-widget:nth-child(n), #footer-widgets .footer-widget .fwidget {
 margin-bottom: 4.5% !important;
 }
}
Code language: CSS (css)