Ajax request type can be set to GET (POST by default)

Before

Ajax requests always use POST.

After

A new httpMethod setting has been added to the Ajax settings. This allows specifying HTTP method used for making the request. This can be used for changing the HTTP method to GET, which makes requests cacheable.

If the httpMethod property is not set, it defaults to POST.

Views now uses GET requests by default when the "Use AJAX" setting is enabled.

Event subscribers

Event subscribers that assume Ajax requests are made using POST request method may need to be updated as well to take into account that Ajax requests may use GET request method.

Before

$request->request->all('ajax_page_state');

After

$request->get('ajax_page_state');