This is a hard one to test as it requires a fairly in-depth knowledge and understanding of the way in which Moodle fetches and stores its strings and templates. Check that the initial prefetch occurs Since pre-fetching only has an noticeable effect if the resources are not already cached in the browser, it is only active when cachejs is enabled. Disable developer mode ( cachejs in particular) Open Moodle to the login page Open developer tools Purge caches via CLI: php admin/cli/purge_caches.php In browser developer tools ensure that the "Network" tab is shown Clear the Network tab and force it to show only XHR requests Refresh the login page Confirm that a short while after the page loaded there were three new requests Look at each request and confirm that you see: core_load_template several strings being fetched in a single query core_output_load_fontawesome Clear the Network tab again Refresh the login page Confirm that you do not see these requests again Run the following in the "Console" tab of the browser tools require(['core/modal_factory'], F => { window.F = F; }); Open the "Network" tab and clear the list of network requests Run the following in the browser console F.create({title: 'test', body: 'body', type: F.types.SAVE_CANCEL}).then(modal => modal.show()); The modal should open immediately Note: if this is tested before MDL-68528 then you will see an extra query because of the lack of normalisation. If you compare this to master before this change, you will see about 8 queries and the modal is slower to open. I'd recommend slowing the connection from the Network tab of your browser to see this in a really pronounced fashion. CI should continue to pass