Hey guys,
is it somehow possible to generate or precache all images of my site, after clearing the cache without open each page one by one?
Thanks for the quick reply. 
I already installed the plugin. But it seems like it doesn’t process images. If you open a page for the first time, it still takes a while to generate the images. I can’t see any improvements for images by using this plugin?
If images are used in content, it should definitely handle those too. It’s basically looping through every page Grav knows about and calling the content() method on it automatically for you. You can also try the CLI command which actually makes and HTTP call to your site and ‘crawls’ it, to ensure each page is hit and therefore cached.
Alright thanks! Looks like it just took a while. Seems to work now!
Can you tell me the cli command, you were talking about?
Take a look at Grav PreCache Plugin CLI Usage