What is the difference between redirect() and header() in CI4?

In CodeIgniter 4, redirect() is the recommended way to perform redirects. It returns a RedirectResponse object: return redirect()->to("https://example.com") or return redirect()->route("users.index"). Pass flash messages: return redirect()->to("/dashboard")->with("success", "Logged in!"). Redirect with old input: return redirect()->back()->withInput(). The redirect() function uses a 302 HTTP status code by default; change with: redirect()->to($url, 301). Using PHP's raw header("Location: $url"); exit bypasses CI4's response object and should be avoided — CI4's redirect properly flushes the response buffer, handles headers already sent, and integrates with the framework's response pipeline. Always return the redirect response from controller methods.