admin/setting/additionalhtml

Additional HTML

These settings allow you to specify HTML that you want added to every page without altering the Moodle code files.

You can add HTML will be added within the HEAD tag for the page, immediately after the BODY tag has been opened, or immediately before the body tag is closed.

Doing this allows you add custom headers or footers on every page, or add support for services like Google Analytics very easily and independent of your chosen theme.

See also

Site appearance menu on Moodle Docs