Does Also Bought modify my theme templates?
The Also Bought app does not need to modify any of your templates to run nicely in your store. We use a Shopify programming feature called ScriptTag (see https://help.shopify.com/en/api/reference/online-store/scripttag for details) that allows our app to be injected dynamically by Shopify when a page loads.
While the ScriptTag feature is very convenient, scripts that run that way have to wait till other content in the page is loaded, what can be perceived as the app being slow.
In order to avoid that and load quickly, we provide the option to insert our app script in your main theme template (theme.liquid). This option is called 'Fast loading' and can be configured in the app preferences page. Please note that this is completely optional, so you can avoid that one-line modification of your theme template by disabling the 'Fast loading' option.
On the other hand, in order to ensure maximum compatibility with some Shopify themes, our app could make minor cosmetic changes on your theme when the app is installed or when the main theme is changed. This is controlled by 'Autoconfigure' option that can be disabled in our app preferences page.
Finally, our app script may be upgraded automatically from time to time to take advantage of the latest features implemented in the app. This can also disabled with the 'Autoconfigure' option.