Code injection is a very important and powerful feature of Ghost.
Ghost allows you to inject code into the top and bottom of your theme files without editing them. This allows for quick modifications to insert useful things like tracking codes and meta tags.
Site Header
Code here will be injected into the {{ghost_head}}
tag on every page of the site.
If you need to add any custom code which should output in your site's head then add that custom code in this section.
This code will be injected in the within the <head>
tag before closing the head tag.
Site footer
Code here will be injected into the {{ghost_foot}}
tag on every page of the site.
This works same as Site header code injection but code in this custom code box are injected in footer before closing the body tag. If you want to inject your custom code within your site footer then use this. Most of the time JavaScript code goes here.