Manually lazy load via functions.php – is it possible?

Hello @thomastolkien

Thank you for contacting us.

About your doubt, this plugin will lazyload all the images and iframes automatically unless they use one of these excluded attributes: https://github.com/wp-media/wp-rocket/blob/trunk/inc/Dependencies/RocketLazyload/Image.php#L391

You don’t need to add a specific class or something similar to make Lazyload plugin to work.

What you can do is exclude images / iframes, but you can’t add images or iframes because they are already added (Unless they have one of the previous attributes)

There are also some images that won’t be lazyloaded, please check these articles:

https://docs.wp-rocket.me/article/278-common-issues-with-lazyload

and

https://docs.wp-rocket.me/article/1141-using-lazyload-in-wp-rocket#background-images

Best regards.