Technically, this is often handled by the browser internal logic suppressing the If-Modified-Since and If-None-Match headers. Furthermore, some browsers may append a Cache-Control: no-cache or Pragma: no-cache header to the request to signal intermediate proxies or the origin server that a fresh copy is required, although the primary mechanism is the local browser ignoring its own store.
Modern browsers allow fine-grained control over refresh behavior via DevTools: shortcut refresh page
The "Shortcut Refresh" forces a complete re-initialization of the page resources. This mechanism instructs the browser to ignore the validity of the local cache for the current request. It bypasses the If-Modified-Since check, instead issuing unconditional GET requests for all resources. This ensures that the user is viewing the most current version of the code and content available on the origin server. Technically, this is often handled by the browser