Once saved, your custom CSS will be safely stored in the WordPress database; this means that there are no data loss concerns relating to theme updates. A child theme isn’t required to safely use SiteOrigin CSS. Your CSS will be outputted into an external stylesheet in the head of your theme and have an ID name of so-css-"theme-name".css. The external stylesheet will be stored in the following location /wp-content/uploads/so-css/.
Please note that SiteOrigin CSS is specific to the activated theme. If you change themes and find SiteOrigin CSS is blank, don’t be alarmed, if you change back to your previous theme, your rules will be available again. SiteOrigin CSS offers the opportunity to create a set of CSS rules for each theme.