diff --git a/Userland/Libraries/LibWeb/HTML/NavigatorID.cpp b/Userland/Libraries/LibWeb/HTML/NavigatorID.cpp
index c757f86bf75..74bcefa5fd9 100644
--- a/Userland/Libraries/LibWeb/HTML/NavigatorID.cpp
+++ b/Userland/Libraries/LibWeb/HTML/NavigatorID.cpp
@@ -11,14 +11,14 @@
 namespace Web::HTML {
 
 // https://html.spec.whatwg.org/multipage/system-state.html#dom-navigator-appversion
-DeprecatedString NavigatorIDMixin::app_version() const
+String NavigatorIDMixin::app_version() const
 {
     // Must return the appropriate string that starts with "5.0 (", as follows:
 
     // Let trail be the substring of default `User-Agent` value that follows the "Mozilla/" prefix.
     auto user_agent_string = ResourceLoader::the().user_agent();
 
-    auto trail = user_agent_string.substring_view(strlen("Mozilla/"), user_agent_string.length() - strlen("Mozilla/"));
+    auto trail = MUST(user_agent_string.substring_from_byte_offset(strlen("Mozilla/"), user_agent_string.bytes().size() - strlen("Mozilla/")));
 
     // If the navigator compatibility mode is Chrome or WebKit
     // NOTE: We are using Chrome for now. Make sure to update all APIs if you add a toggle for this.
@@ -33,7 +33,7 @@ DeprecatedString NavigatorIDMixin::app_version() const
 }
 
 // https://html.spec.whatwg.org/multipage/system-state.html#dom-navigator-platform
-DeprecatedString NavigatorIDMixin::platform() const
+String NavigatorIDMixin::platform() const
 {
     // Must return a string representing the platform on which the browser is executing (e.g. "MacIntel", "Win32",
     // "Linux x86_64", "Linux armv81") or, for privacy and compatibility, a string that is commonly returned on another
@@ -44,7 +44,7 @@ DeprecatedString NavigatorIDMixin::platform() const
 }
 
 // https://html.spec.whatwg.org/multipage/system-state.html#dom-navigator-useragent
-DeprecatedString NavigatorIDMixin::user_agent() const
+String NavigatorIDMixin::user_agent() const
 {
     // Must return the default `User-Agent` value.
     return ResourceLoader::the().user_agent();
diff --git a/Userland/Libraries/LibWeb/HTML/NavigatorID.h b/Userland/Libraries/LibWeb/HTML/NavigatorID.h
index 31cf0568f99..93ff9981cd6 100644
--- a/Userland/Libraries/LibWeb/HTML/NavigatorID.h
+++ b/Userland/Libraries/LibWeb/HTML/NavigatorID.h
@@ -6,7 +6,7 @@
 
 #pragma once
 
-#include <AK/DeprecatedString.h>
+#include <AK/String.h>
 
 namespace Web::HTML {
 
@@ -17,31 +17,31 @@ public:
     // implementers are strongly urged to include as little information in this API as possible.
 
     // https://html.spec.whatwg.org/multipage/system-state.html#dom-navigator-appcodename
-    DeprecatedString app_code_name() const { return "Mozilla"sv; }
+    String app_code_name() const { return "Mozilla"_string; }
 
     // https://html.spec.whatwg.org/multipage/system-state.html#dom-navigator-appcodename
-    DeprecatedString app_name() const { return "Netscape"sv; }
+    String app_name() const { return "Netscape"_string; }
 
     // https://html.spec.whatwg.org/multipage/system-state.html#dom-navigator-appversion
-    DeprecatedString app_version() const;
+    String app_version() const;
 
     // https://html.spec.whatwg.org/multipage/system-state.html#dom-navigator-platform
-    DeprecatedString platform() const;
+    String platform() const;
 
     // https://html.spec.whatwg.org/multipage/system-state.html#dom-navigator-product
-    DeprecatedString product() const { return "Gecko"sv; }
+    String product() const { return "Gecko"_string; }
 
     // https://html.spec.whatwg.org/multipage/system-state.html#dom-navigator-productsub
-    DeprecatedString product_sub() const { return "20030107"sv; } // Compatibility mode "Chrome"
+    String product_sub() const { return "20030107"_string; } // Compatibility mode "Chrome"
 
     // https://html.spec.whatwg.org/multipage/system-state.html#dom-navigator-useragent
-    DeprecatedString user_agent() const;
+    String user_agent() const;
 
     // https://html.spec.whatwg.org/multipage/system-state.html#dom-navigator-vendor
-    DeprecatedString vendor() const { return "Google Inc."sv; } // Compatibility mode "Chrome"
+    String vendor() const { return "Google Inc."_string; } // Compatibility mode "Chrome"
 
     // https://html.spec.whatwg.org/multipage/system-state.html#dom-navigator-vendorsub
-    DeprecatedString vendor_sub() const { return ""sv; }
+    String vendor_sub() const { return String {}; }
 
     // NOTE: If the navigator compatibility mode is Gecko, then the user agent must also support the following partial interface:
     //       bool taint_enabled()
diff --git a/Userland/Libraries/LibWeb/Loader/ResourceLoader.cpp b/Userland/Libraries/LibWeb/Loader/ResourceLoader.cpp
index 74f0893dba7..352aa62fecc 100644
--- a/Userland/Libraries/LibWeb/Loader/ResourceLoader.cpp
+++ b/Userland/Libraries/LibWeb/Loader/ResourceLoader.cpp
@@ -59,8 +59,8 @@ ErrorOr<NonnullRefPtr<ResourceLoader>> ResourceLoader::try_create(NonnullRefPtr<
 
 ResourceLoader::ResourceLoader(NonnullRefPtr<ResourceLoaderConnector> connector)
     : m_connector(move(connector))
-    , m_user_agent(default_user_agent)
-    , m_platform(default_platform)
+    , m_user_agent(MUST(String::from_utf8(default_user_agent)))
+    , m_platform(MUST(String::from_utf8(default_platform)))
 {
 }
 
@@ -315,7 +315,7 @@ void ResourceLoader::load(LoadRequest& request, SuccessCallback success_callback
         auto proxy = ProxyMappings::the().proxy_for_url(url);
 
         HashMap<DeprecatedString, DeprecatedString> headers;
-        headers.set("User-Agent", m_user_agent);
+        headers.set("User-Agent", m_user_agent.to_deprecated_string());
         headers.set("Accept-Encoding", "gzip, deflate, br");
 
         for (auto& it : request.headers()) {
diff --git a/Userland/Libraries/LibWeb/Loader/ResourceLoader.h b/Userland/Libraries/LibWeb/Loader/ResourceLoader.h
index 25e21e22242..85e99726727 100644
--- a/Userland/Libraries/LibWeb/Loader/ResourceLoader.h
+++ b/Userland/Libraries/LibWeb/Loader/ResourceLoader.h
@@ -123,11 +123,11 @@ public:
 
     int pending_loads() const { return m_pending_loads; }
 
-    DeprecatedString const& user_agent() const { return m_user_agent; }
-    void set_user_agent(DeprecatedString const& user_agent) { m_user_agent = user_agent; }
+    String const& user_agent() const { return m_user_agent; }
+    void set_user_agent(String user_agent) { m_user_agent = move(user_agent); }
 
-    DeprecatedString const& platform() const { return m_platform; }
-    void set_platform(DeprecatedString const& platform) { m_platform = platform; }
+    String const& platform() const { return m_platform; }
+    void set_platform(String platform) { m_platform = move(platform); }
 
     void clear_cache();
     void evict_from_cache(LoadRequest const&);
@@ -142,8 +142,8 @@ private:
 
     HashTable<NonnullRefPtr<ResourceLoaderConnectorRequest>> m_active_requests;
     NonnullRefPtr<ResourceLoaderConnector> m_connector;
-    DeprecatedString m_user_agent;
-    DeprecatedString m_platform;
+    String m_user_agent;
+    String m_platform;
     Optional<Page&> m_page {};
 };
 
diff --git a/Userland/Services/WebContent/ConnectionFromClient.cpp b/Userland/Services/WebContent/ConnectionFromClient.cpp
index 5a0f35c72bb..3af096a0680 100644
--- a/Userland/Services/WebContent/ConnectionFromClient.cpp
+++ b/Userland/Services/WebContent/ConnectionFromClient.cpp
@@ -451,7 +451,7 @@ void ConnectionFromClient::debug_request(DeprecatedString const& request, Deprec
     }
 
     if (request == "spoof-user-agent") {
-        Web::ResourceLoader::the().set_user_agent(argument);
+        Web::ResourceLoader::the().set_user_agent(MUST(String::from_deprecated_string(argument)));
         return;
     }