diff --git a/Libraries/LibWeb/CMakeLists.txt b/Libraries/LibWeb/CMakeLists.txt
index 4de4cd68c44..97dcd2497eb 100644
--- a/Libraries/LibWeb/CMakeLists.txt
+++ b/Libraries/LibWeb/CMakeLists.txt
@@ -681,6 +681,7 @@ set(SOURCES
     Painting/VideoPaintable.cpp
     Painting/ViewportPaintable.cpp
     PerformanceTimeline/EntryTypes.cpp
+    PerformanceTimeline/EventNames.cpp
     PerformanceTimeline/PerformanceEntry.cpp
     PerformanceTimeline/PerformanceObserver.cpp
     PerformanceTimeline/PerformanceObserverEntryList.cpp
@@ -701,6 +702,7 @@ set(SOURCES
     ResizeObserver/ResizeObserver.cpp
     ResizeObserver/ResizeObserverEntry.cpp
     ResizeObserver/ResizeObserverSize.cpp
+    ResourceTiming/PerformanceResourceTiming.cpp
     SecureContexts/AbstractOperations.cpp
     ServiceWorker/Job.cpp
     ServiceWorker/Registration.cpp
diff --git a/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp b/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp
index 97b5ff3cd0a..4d382b74974 100644
--- a/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp
+++ b/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp
@@ -53,6 +53,7 @@
 #include <LibWeb/MixedContent/AbstractOperations.h>
 #include <LibWeb/Platform/EventLoopPlugin.h>
 #include <LibWeb/ReferrerPolicy/AbstractOperations.h>
+#include <LibWeb/ResourceTiming/PerformanceResourceTiming.h>
 #include <LibWeb/SRI/SRI.h>
 #include <LibWeb/SecureContexts/AbstractOperations.h>
 #include <LibWeb/Streams/TransformStream.h>
@@ -687,13 +688,11 @@ void fetch_response_handover(JS::Realm& realm, Infrastructure::FetchParams const
                     body_info.content_type = MimeSniff::minimise_a_supported_mime_type(mime_type.value());
             }
 
-            // FIXME: 8. If fetchParams’s request’s initiator type is not null, then mark resource timing given timingInfo,
-            //           request’s URL, request’s initiator type, global, cacheState, bodyInfo, and responseStatus.
-            (void)timing_info;
-            (void)global;
-            (void)cache_state;
-            (void)body_info;
-            (void)response_status;
+            // 8. If fetchParams’s request’s initiator type is not null, then mark resource timing given timingInfo,
+            //    request’s URL, request’s initiator type, global, cacheState, bodyInfo, and responseStatus.
+            if (fetch_params.request()->initiator_type().has_value()) {
+                ResourceTiming::PerformanceResourceTiming::mark_resource_timing(timing_info, fetch_params.request()->url().to_string(), Infrastructure::initiator_type_to_string(fetch_params.request()->initiator_type().value()), global, cache_state, body_info, response_status);
+            }
         });
 
         // 4. Let processResponseEndOfBodyTask be the following steps:
diff --git a/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Requests.cpp b/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Requests.cpp
index c6b3b030182..c1fb681660b 100644
--- a/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Requests.cpp
+++ b/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Requests.cpp
@@ -442,6 +442,55 @@ StringView request_mode_to_string(Request::Mode mode)
     VERIFY_NOT_REACHED();
 }
 
+FlyString initiator_type_to_string(Request::InitiatorType initiator_type)
+{
+    switch (initiator_type) {
+    case Request::InitiatorType::Audio:
+        return "audio"_fly_string;
+    case Request::InitiatorType::Beacon:
+        return "beacon"_fly_string;
+    case Request::InitiatorType::Body:
+        return "body"_fly_string;
+    case Request::InitiatorType::CSS:
+        return "css"_fly_string;
+    case Request::InitiatorType::EarlyHint:
+        return "early-hints"_fly_string;
+    case Request::InitiatorType::Embed:
+        return "embed"_fly_string;
+    case Request::InitiatorType::Fetch:
+        return "fetch"_fly_string;
+    case Request::InitiatorType::Font:
+        return "font"_fly_string;
+    case Request::InitiatorType::Frame:
+        return "frame"_fly_string;
+    case Request::InitiatorType::IFrame:
+        return "iframe"_fly_string;
+    case Request::InitiatorType::Image:
+        return "image"_fly_string;
+    case Request::InitiatorType::IMG:
+        return "img"_fly_string;
+    case Request::InitiatorType::Input:
+        return "input"_fly_string;
+    case Request::InitiatorType::Link:
+        return "link"_fly_string;
+    case Request::InitiatorType::Object:
+        return "object"_fly_string;
+    case Request::InitiatorType::Ping:
+        return "ping"_fly_string;
+    case Request::InitiatorType::Script:
+        return "script"_fly_string;
+    case Request::InitiatorType::Track:
+        return "track"_fly_string;
+    case Request::InitiatorType::Video:
+        return "video"_fly_string;
+    case Request::InitiatorType::XMLHttpRequest:
+        return "xmlhttprequest"_fly_string;
+    case Request::InitiatorType::Other:
+        return "other"_fly_string;
+    }
+    VERIFY_NOT_REACHED();
+}
+
 Optional<Request::Priority> request_priority_from_string(StringView string)
 {
     if (string.equals_ignoring_ascii_case("high"sv))
diff --git a/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Requests.h b/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Requests.h
index b113ccd343c..b9504ca4f64 100644
--- a/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Requests.h
+++ b/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Requests.h
@@ -531,6 +531,7 @@ private:
 
 StringView request_destination_to_string(Request::Destination);
 StringView request_mode_to_string(Request::Mode);
+FlyString initiator_type_to_string(Request::InitiatorType);
 
 Optional<Request::Priority> request_priority_from_string(StringView);
 
diff --git a/Libraries/LibWeb/Forward.h b/Libraries/LibWeb/Forward.h
index ec6d824c740..a4a2a106cf8 100644
--- a/Libraries/LibWeb/Forward.h
+++ b/Libraries/LibWeb/Forward.h
@@ -74,6 +74,7 @@ enum class MediaEncodingType : u8;
 enum class MediaKeysRequirement : u8;
 enum class ReadableStreamReaderMode : u8;
 enum class ReferrerPolicy : u8;
+enum class RenderBlockingStatusType : u8;
 enum class RequestCache : u8;
 enum class RequestCredentials : u8;
 enum class RequestDestination : u8;
@@ -756,6 +757,10 @@ namespace Web::ResizeObserver {
 class ResizeObserver;
 }
 
+namespace Web::ResourceTiming {
+class PerformanceResourceTiming;
+}
+
 namespace Web::Selection {
 class Selection;
 }
diff --git a/Libraries/LibWeb/HTML/WindowOrWorkerGlobalScope.cpp b/Libraries/LibWeb/HTML/WindowOrWorkerGlobalScope.cpp
index ce192ee89fe..88918547c88 100644
--- a/Libraries/LibWeb/HTML/WindowOrWorkerGlobalScope.cpp
+++ b/Libraries/LibWeb/HTML/WindowOrWorkerGlobalScope.cpp
@@ -34,10 +34,12 @@
 #include <LibWeb/IndexedDB/IDBFactory.h>
 #include <LibWeb/Infra/Strings.h>
 #include <LibWeb/PerformanceTimeline/EntryTypes.h>
+#include <LibWeb/PerformanceTimeline/EventNames.h>
 #include <LibWeb/PerformanceTimeline/PerformanceObserver.h>
 #include <LibWeb/PerformanceTimeline/PerformanceObserverEntryList.h>
 #include <LibWeb/Platform/EventLoopPlugin.h>
 #include <LibWeb/Platform/ImageCodecPlugin.h>
+#include <LibWeb/ResourceTiming/PerformanceResourceTiming.h>
 #include <LibWeb/UserTiming/PerformanceMark.h>
 #include <LibWeb/UserTiming/PerformanceMeasure.h>
 #include <LibWeb/WebIDL/AbstractOperations.h>
@@ -75,6 +77,7 @@ void WindowOrWorkerGlobalScopeMixin::visit_edges(JS::Cell::Visitor& visitor)
         entry.value.visit_edges(visitor);
     visitor.visit(m_registered_event_sources);
     visitor.visit(m_crypto);
+    visitor.visit(m_resource_timing_secondary_buffer);
 }
 
 void WindowOrWorkerGlobalScopeMixin::finalize()
@@ -472,7 +475,6 @@ void WindowOrWorkerGlobalScopeMixin::add_performance_entry(GC::Ref<PerformanceTi
         tuple.performance_entry_buffer.append(new_entry);
 }
 
-
 void WindowOrWorkerGlobalScopeMixin::clear_performance_entry_buffer(Badge<HighResolutionTime::Performance>, FlyString const& entry_type)
 {
     auto& tuple = relevant_performance_entry_tuple(entry_type);
@@ -643,6 +645,102 @@ void WindowOrWorkerGlobalScopeMixin::queue_the_performance_observer_task()
     }));
 }
 
+// https://w3c.github.io/resource-timing/#dfn-add-a-performanceresourcetiming-entry
+void WindowOrWorkerGlobalScopeMixin::add_resource_timing_entry(Badge<ResourceTiming::PerformanceResourceTiming>, GC::Ref<ResourceTiming::PerformanceResourceTiming> entry)
+{
+    // 1. If can add resource timing entry returns true and resource timing buffer full event pending flag is false,
+    //    run the following substeps:
+    if (can_add_resource_timing_entry() && !m_resource_timing_buffer_full_event_pending) {
+        // a. Add new entry to the performance entry buffer.
+        // b. Increase resource timing buffer current size by 1.
+        add_performance_entry(entry);
+
+        // c. Return.
+        return;
+    }
+
+    // 2. If resource timing buffer full event pending flag is false, run the following substeps:
+    if (!m_resource_timing_buffer_full_event_pending) {
+        // a. Set resource timing buffer full event pending flag to true.
+        m_resource_timing_buffer_full_event_pending = true;
+
+        // b. Queue a task on the performance timeline task source to run fire a buffer full event.
+        HTML::queue_a_task(HTML::Task::Source::PerformanceTimeline, nullptr, nullptr, GC::create_function(this_impl().heap(), [this] {
+            fire_resource_timing_buffer_full_event();
+        }));
+    }
+
+    // 3. Add new entry to the resource timing secondary buffer.
+    // 4. Increase resource timing secondary buffer current size by 1.
+    m_resource_timing_secondary_buffer.append(entry);
+}
+
+// https://w3c.github.io/resource-timing/#dfn-can-add-resource-timing-entry
+bool WindowOrWorkerGlobalScopeMixin::can_add_resource_timing_entry()
+{
+    // 1. If resource timing buffer current size is smaller than resource timing buffer size limit, return true.
+    // 2. Return false.
+    return resource_timing_buffer_current_size() < m_resource_timing_buffer_size_limit;
+}
+
+// https://w3c.github.io/resource-timing/#dfn-resource-timing-buffer-current-size
+size_t WindowOrWorkerGlobalScopeMixin::resource_timing_buffer_current_size()
+{
+    // A resource timing buffer current size which is initially 0.
+    auto resource_timing_tuple = relevant_performance_entry_tuple(PerformanceTimeline::EntryTypes::resource);
+    return resource_timing_tuple.performance_entry_buffer.size();
+}
+
+// https://w3c.github.io/resource-timing/#dfn-fire-a-buffer-full-event
+void WindowOrWorkerGlobalScopeMixin::fire_resource_timing_buffer_full_event()
+{
+    // 1. While resource timing secondary buffer is not empty, run the following substeps:
+    while (!m_resource_timing_secondary_buffer.is_empty()) {
+        // 1. Let number of excess entries before be resource timing secondary buffer current size.
+        auto number_of_excess_entries_before = m_resource_timing_secondary_buffer.size();
+
+        // 2. If can add resource timing entry returns false, then fire an event named resourcetimingbufferfull at the Performance object.
+        if (!can_add_resource_timing_entry()) {
+            auto full_event = DOM::Event::create(this_impl().realm(), PerformanceTimeline::EventNames::resourcetimingbufferfull);
+            performance()->dispatch_event(full_event);
+        }
+
+        // 3. Run copy secondary buffer.
+        copy_resource_timing_secondary_buffer();
+
+        // 4. Let number of excess entries after be resource timing secondary buffer current size.
+        auto number_of_excess_entries_after = m_resource_timing_secondary_buffer.size();
+
+        // 5. If number of excess entries before is lower than or equals number of excess entries after, then remove
+        //    all entries from resource timing secondary buffer, set resource timing secondary buffer current size to
+        //    0, and abort these steps.
+        if (number_of_excess_entries_before <= number_of_excess_entries_after) {
+            m_resource_timing_secondary_buffer.clear();
+            break;
+        }
+    }
+
+    // 2. Set resource timing buffer full event pending flag to false.
+    m_resource_timing_buffer_full_event_pending = false;
+}
+
+// https://w3c.github.io/resource-timing/#dfn-copy-secondary-buffer
+void WindowOrWorkerGlobalScopeMixin::copy_resource_timing_secondary_buffer()
+{
+    // 1. While resource timing secondary buffer is not empty and can add resource timing entry returns true,
+    //    run the following substeps:
+    while (!m_resource_timing_secondary_buffer.is_empty() && can_add_resource_timing_entry()) {
+        // 1. Let entry be the oldest PerformanceResourceTiming in resource timing secondary buffer.
+        // 2. Add entry to the end of performance entry buffer.
+        // 3. Increment resource timing buffer current size by 1.
+        // 4. Remove entry from resource timing secondary buffer.
+        // 5. Decrement resource timing secondary buffer current size by 1.
+        auto entry = m_resource_timing_secondary_buffer.take_first();
+        auto& resource_tuple = relevant_performance_entry_tuple(PerformanceTimeline::EntryTypes::resource);
+        resource_tuple.performance_entry_buffer.append(entry);
+    }
+}
+
 void WindowOrWorkerGlobalScopeMixin::register_event_source(Badge<EventSource>, GC::Ref<EventSource> event_source)
 {
     m_registered_event_sources.set(event_source);
diff --git a/Libraries/LibWeb/HTML/WindowOrWorkerGlobalScope.h b/Libraries/LibWeb/HTML/WindowOrWorkerGlobalScope.h
index 154574f992c..782b8eda58f 100644
--- a/Libraries/LibWeb/HTML/WindowOrWorkerGlobalScope.h
+++ b/Libraries/LibWeb/HTML/WindowOrWorkerGlobalScope.h
@@ -66,6 +66,9 @@ public:
 
     void queue_the_performance_observer_task();
 
+    void set_resource_timing_buffer_size_limit(Badge<HighResolutionTime::Performance>, u32 value) { m_resource_timing_buffer_size_limit = value; }
+    void add_resource_timing_entry(Badge<ResourceTiming::PerformanceResourceTiming>, GC::Ref<ResourceTiming::PerformanceResourceTiming> entry);
+
     void register_event_source(Badge<EventSource>, GC::Ref<EventSource>);
     void unregister_event_source(Badge<EventSource>, GC::Ref<EventSource>);
     void forcibly_close_all_event_sources();
@@ -112,6 +115,11 @@ private:
 
     GC::Ref<WebIDL::Promise> create_image_bitmap_impl(ImageBitmapSource& image, Optional<WebIDL::Long> sx, Optional<WebIDL::Long> sy, Optional<WebIDL::Long> sw, Optional<WebIDL::Long> sh, Optional<ImageBitmapOptions>& options) const;
 
+    size_t resource_timing_buffer_current_size();
+    bool can_add_resource_timing_entry();
+    void fire_resource_timing_buffer_full_event();
+    void copy_resource_timing_secondary_buffer();
+
     IDAllocator m_timer_id_allocator;
     HashMap<int, GC::Ref<Timer>> m_timers;
 
@@ -141,6 +149,24 @@ private:
     bool m_error_reporting_mode { false };
 
     WebSockets::WebSocket::List m_registered_web_sockets;
+
+    // https://w3c.github.io/resource-timing/#sec-extensions-performance-interface
+    // Each ECMAScript global environment has:
+    // https://w3c.github.io/resource-timing/#dfn-resource-timing-buffer-size-limit
+    // A resource timing buffer size limit which should initially be 250 or greater.
+    // The recommended minimum number of PerformanceResourceTiming objects is 250, though this may be changed by the
+    // user agent. setResourceTimingBufferSize can be called to request a change to this limit.
+    u32 m_resource_timing_buffer_size_limit { 250 };
+
+    // https://w3c.github.io/resource-timing/#dfn-resource-timing-buffer-full-event-pending-flag
+    // A resource timing buffer full event pending flag which is initially false.
+    bool m_resource_timing_buffer_full_event_pending { false };
+
+    // https://w3c.github.io/resource-timing/#dfn-resource-timing-secondary-buffer-current-size
+    // A resource timing secondary buffer current size which is initially 0.
+    // https://w3c.github.io/resource-timing/#dfn-resource-timing-secondary-buffer
+    // A resource timing secondary buffer to store PerformanceResourceTiming objects that is initially empty.
+    Vector<GC::Ref<ResourceTiming::PerformanceResourceTiming>> m_resource_timing_secondary_buffer;
 };
 
 }
diff --git a/Libraries/LibWeb/HighResolutionTime/Performance.cpp b/Libraries/LibWeb/HighResolutionTime/Performance.cpp
index d9be79f28e0..7ab3df295cf 100644
--- a/Libraries/LibWeb/HighResolutionTime/Performance.cpp
+++ b/Libraries/LibWeb/HighResolutionTime/Performance.cpp
@@ -17,6 +17,7 @@
 #include <LibWeb/NavigationTiming/PerformanceNavigation.h>
 #include <LibWeb/NavigationTiming/PerformanceTiming.h>
 #include <LibWeb/PerformanceTimeline/EntryTypes.h>
+#include <LibWeb/PerformanceTimeline/EventNames.h>
 
 namespace Web::HighResolutionTime {
 
@@ -330,6 +331,35 @@ void Performance::clear_measures(Optional<String> measure_name)
     // 3. Return undefined.
 }
 
+// https://w3c.github.io/resource-timing/#dom-performance-clearresourcetimings
+void Performance::clear_resource_timings()
+{
+    // 1. Remove all PerformanceResourceTiming objects in the performance entry buffer.
+    // 2. Set resource timing buffer current size to 0.
+    window_or_worker().clear_performance_entry_buffer({}, PerformanceTimeline::EntryTypes::resource);
+}
+
+// https://w3c.github.io/resource-timing/#dom-performance-setresourcetimingbuffersize
+void Performance::set_resource_timing_buffer_size(u32 max_size)
+{
+    // 1. Set resource timing buffer size limit to the maxSize parameter. If the maxSize parameter is less than
+    //    resource timing buffer current size, no PerformanceResourceTiming objects are to be removed from the
+    //    performance entry buffer.
+    window_or_worker().set_resource_timing_buffer_size_limit({}, max_size);
+}
+
+// https://w3c.github.io/resource-timing/#dom-performance-onresourcetimingbufferfull
+void Performance::set_onresourcetimingbufferfull(WebIDL::CallbackType* event_handler)
+{
+    set_event_handler_attribute(PerformanceTimeline::EventNames::resourcetimingbufferfull, event_handler);
+}
+
+// https://w3c.github.io/resource-timing/#dom-performance-onresourcetimingbufferfull
+WebIDL::CallbackType* Performance::onresourcetimingbufferfull()
+{
+    return event_handler_attribute(PerformanceTimeline::EventNames::resourcetimingbufferfull);
+}
+
 // https://www.w3.org/TR/performance-timeline/#getentries-method
 WebIDL::ExceptionOr<Vector<GC::Root<PerformanceTimeline::PerformanceEntry>>> Performance::get_entries() const
 {
diff --git a/Libraries/LibWeb/HighResolutionTime/Performance.h b/Libraries/LibWeb/HighResolutionTime/Performance.h
index 799f61143f0..62f342c2faa 100644
--- a/Libraries/LibWeb/HighResolutionTime/Performance.h
+++ b/Libraries/LibWeb/HighResolutionTime/Performance.h
@@ -30,6 +30,11 @@ public:
     WebIDL::ExceptionOr<GC::Ref<UserTiming::PerformanceMeasure>> measure(String const& measure_name, Variant<String, UserTiming::PerformanceMeasureOptions> const& start_or_measure_options, Optional<String> end_mark);
     void clear_measures(Optional<String> measure_name);
 
+    void clear_resource_timings();
+    void set_resource_timing_buffer_size(u32 max_size);
+    void set_onresourcetimingbufferfull(WebIDL::CallbackType*);
+    WebIDL::CallbackType* onresourcetimingbufferfull();
+
     WebIDL::ExceptionOr<Vector<GC::Root<PerformanceTimeline::PerformanceEntry>>> get_entries() const;
     WebIDL::ExceptionOr<Vector<GC::Root<PerformanceTimeline::PerformanceEntry>>> get_entries_by_type(String const& type) const;
     WebIDL::ExceptionOr<Vector<GC::Root<PerformanceTimeline::PerformanceEntry>>> get_entries_by_name(String const& name, Optional<String> type) const;
diff --git a/Libraries/LibWeb/HighResolutionTime/Performance.idl b/Libraries/LibWeb/HighResolutionTime/Performance.idl
index e619f01f337..0ee1307bde7 100644
--- a/Libraries/LibWeb/HighResolutionTime/Performance.idl
+++ b/Libraries/LibWeb/HighResolutionTime/Performance.idl
@@ -23,6 +23,12 @@ interface Performance : EventTarget {
     PerformanceMeasure measure(DOMString measureName, optional (DOMString or PerformanceMeasureOptions) startOrMeasureOptions = {}, optional DOMString endMark);
     undefined clearMeasures(optional DOMString measureName);
 
+    // https://w3c.github.io/resource-timing/#sec-extensions-performance-interface
+    // "Resource Timing" extensions to the Performance interface
+    undefined clearResourceTimings();
+    undefined setResourceTimingBufferSize(unsigned long maxSize);
+    attribute EventHandler onresourcetimingbufferfull;
+
     // https://www.w3.org/TR/performance-timeline/#extensions-to-the-performance-interface
     // "Performance Timeline" extensions to the Performance interface
     PerformanceEntryList getEntries();
diff --git a/Libraries/LibWeb/HighResolutionTime/SupportedPerformanceTypes.h b/Libraries/LibWeb/HighResolutionTime/SupportedPerformanceTypes.h
index 55e02ccf410..ab991130e5b 100644
--- a/Libraries/LibWeb/HighResolutionTime/SupportedPerformanceTypes.h
+++ b/Libraries/LibWeb/HighResolutionTime/SupportedPerformanceTypes.h
@@ -9,8 +9,9 @@
 namespace Web::HighResolutionTime {
 
 // Please keep these in alphabetical order based on the entry type :^)
-#define ENUMERATE_SUPPORTED_PERFORMANCE_ENTRY_TYPES                                                                   \
-    __ENUMERATE_SUPPORTED_PERFORMANCE_ENTRY_TYPES(PerformanceTimeline::EntryTypes::mark, UserTiming::PerformanceMark) \
-    __ENUMERATE_SUPPORTED_PERFORMANCE_ENTRY_TYPES(PerformanceTimeline::EntryTypes::measure, UserTiming::PerformanceMeasure)
+#define ENUMERATE_SUPPORTED_PERFORMANCE_ENTRY_TYPES                                                                         \
+    __ENUMERATE_SUPPORTED_PERFORMANCE_ENTRY_TYPES(PerformanceTimeline::EntryTypes::mark, UserTiming::PerformanceMark)       \
+    __ENUMERATE_SUPPORTED_PERFORMANCE_ENTRY_TYPES(PerformanceTimeline::EntryTypes::measure, UserTiming::PerformanceMeasure) \
+    __ENUMERATE_SUPPORTED_PERFORMANCE_ENTRY_TYPES(PerformanceTimeline::EntryTypes::resource, ResourceTiming::PerformanceResourceTiming)
 
 }
diff --git a/Libraries/LibWeb/PerformanceTimeline/EventNames.cpp b/Libraries/LibWeb/PerformanceTimeline/EventNames.cpp
new file mode 100644
index 00000000000..40f882a2d13
--- /dev/null
+++ b/Libraries/LibWeb/PerformanceTimeline/EventNames.cpp
@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2025, Luke Wilde <luke@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/PerformanceTimeline/EventNames.h>
+
+namespace Web::PerformanceTimeline::EventNames {
+
+#define __ENUMERATE_PERFORMANCE_TIMELINE_EVENT(name) \
+    FlyString name = #name##_fly_string;
+ENUMERATE_PERFORMANCE_TIMELINE_EVENTS
+#undef __ENUMERATE_PERFORMANCE_TIMELINE_EVENT
+
+}
diff --git a/Libraries/LibWeb/PerformanceTimeline/EventNames.h b/Libraries/LibWeb/PerformanceTimeline/EventNames.h
new file mode 100644
index 00000000000..82d33c41c2e
--- /dev/null
+++ b/Libraries/LibWeb/PerformanceTimeline/EventNames.h
@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2025, Luke Wilde <luke@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/FlyString.h>
+
+namespace Web::PerformanceTimeline::EventNames {
+
+#define ENUMERATE_PERFORMANCE_TIMELINE_EVENTS \
+    __ENUMERATE_PERFORMANCE_TIMELINE_EVENT(resourcetimingbufferfull)
+
+#define __ENUMERATE_PERFORMANCE_TIMELINE_EVENT(name) extern FlyString name;
+ENUMERATE_PERFORMANCE_TIMELINE_EVENTS
+#undef __ENUMERATE_PERFORMANCE_TIMELINE_EVENT
+
+}
diff --git a/Libraries/LibWeb/ResourceTiming/PerformanceResourceTiming.cpp b/Libraries/LibWeb/ResourceTiming/PerformanceResourceTiming.cpp
new file mode 100644
index 00000000000..bca0239883b
--- /dev/null
+++ b/Libraries/LibWeb/ResourceTiming/PerformanceResourceTiming.cpp
@@ -0,0 +1,340 @@
+/*
+ * Copyright (c) 2025, Luke Wilde <lukew@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/Bindings/Intrinsics.h>
+#include <LibWeb/Fetch/Infrastructure/FetchTimingInfo.h>
+#include <LibWeb/HTML/WindowOrWorkerGlobalScope.h>
+#include <LibWeb/HighResolutionTime/TimeOrigin.h>
+#include <LibWeb/PerformanceTimeline/EntryTypes.h>
+#include <LibWeb/ResourceTiming/PerformanceResourceTiming.h>
+
+namespace Web::ResourceTiming {
+
+GC_DEFINE_ALLOCATOR(PerformanceResourceTiming);
+
+PerformanceResourceTiming::PerformanceResourceTiming(JS::Realm& realm, String const& name, HighResolutionTime::DOMHighResTimeStamp start_time, HighResolutionTime::DOMHighResTimeStamp duration, GC::Ref<Fetch::Infrastructure::FetchTimingInfo> timing_info)
+    : PerformanceTimeline::PerformanceEntry(realm, name, start_time, duration)
+    , m_timing_info(timing_info)
+{
+}
+
+PerformanceResourceTiming::~PerformanceResourceTiming() = default;
+
+// https://w3c.github.io/resource-timing/#dfn-entrytype
+FlyString const& PerformanceResourceTiming::entry_type() const
+{
+    // entryType
+    //  The entryType getter steps are to return the DOMString "resource".
+    return PerformanceTimeline::EntryTypes::resource;
+}
+
+void PerformanceResourceTiming::initialize(JS::Realm& realm)
+{
+    Base::initialize(realm);
+    WEB_SET_PROTOTYPE_FOR_INTERFACE(PerformanceResourceTiming);
+}
+
+void PerformanceResourceTiming::visit_edges(JS::Cell::Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+    visitor.visit(m_timing_info);
+}
+
+// https://w3c.github.io/resource-timing/#dfn-convert-fetch-timestamp
+HighResolutionTime::DOMHighResTimeStamp convert_fetch_timestamp(HighResolutionTime::DOMHighResTimeStamp time_stamp, JS::Object const& global)
+{
+    // 1. If ts is zero, return zero.
+    if (time_stamp == 0.0)
+        return 0.0;
+
+    // 2. Otherwise, return the relative high resolution coarse time given ts and global.
+    return HighResolutionTime::relative_high_resolution_coarsen_time(time_stamp, global);
+}
+
+// https://w3c.github.io/resource-timing/#dfn-mark-resource-timing
+void PerformanceResourceTiming::mark_resource_timing(GC::Ref<Fetch::Infrastructure::FetchTimingInfo> timing_info, String const& requested_url, FlyString const& initiator_type, JS::Object& global, Optional<Fetch::Infrastructure::Response::CacheState> const& cache_mode, Fetch::Infrastructure::Response::BodyInfo body_info, Fetch::Infrastructure::Status response_status, FlyString delivery_type)
+{
+    // 1. Create a PerformanceResourceTiming object entry in global's realm.
+    auto& window_or_worker = as<HTML::WindowOrWorkerGlobalScopeMixin>(global);
+    auto& realm = window_or_worker.this_impl().realm();
+
+    // https://w3c.github.io/resource-timing/#dfn-name
+    // name
+    //  The name getter steps are to return this's requested URL.
+
+    // https://w3c.github.io/resource-timing/#dfn-starttime
+    // startTime
+    //  The startTime getter steps are to convert fetch timestamp for this's timing info's start time and this's relevant global object.
+
+    // https://w3c.github.io/resource-timing/#dfn-duration
+    // duration
+    //  The duration getter steps are to return this's timing info's end time minus this's timing info's start time.
+    auto converted_start_time = convert_fetch_timestamp(timing_info->start_time(), global);
+    auto converted_end_time = convert_fetch_timestamp(timing_info->end_time(), global);
+    auto entry = realm.create<PerformanceResourceTiming>(realm, requested_url, converted_start_time, converted_end_time - converted_start_time, timing_info);
+
+    // Setup the resource timing entry for entry, given initiatorType, requestedURL, timingInfo, cacheMode, bodyInfo, responseStatus, and deliveryType.
+    entry->setup_the_resource_timing_entry(initiator_type, requested_url, timing_info, cache_mode, move(body_info), response_status, delivery_type);
+
+    // 3. Queue entry.
+    window_or_worker.queue_performance_entry(entry);
+
+    // 4. Add entry to global's performance entry buffer.
+    window_or_worker.add_resource_timing_entry({}, entry);
+}
+
+// https://www.w3.org/TR/resource-timing/#dfn-setup-the-resource-timing-entry
+void PerformanceResourceTiming::setup_the_resource_timing_entry(FlyString const& initiator_type, String const& requested_url, GC::Ref<Fetch::Infrastructure::FetchTimingInfo> timing_info, Optional<Fetch::Infrastructure::Response::CacheState> const& cache_mode, Fetch::Infrastructure::Response::BodyInfo body_info, Fetch::Infrastructure::Status response_status, FlyString delivery_type)
+{
+    // 2. Setup the resource timing entry for entry, given initiatorType, requestedURL, timingInfo, cacheMode, bodyInfo, responseStatus, and deliveryType.
+    // https://w3c.github.io/resource-timing/#dfn-setup-the-resource-timing-entry
+
+    // 1. Assert that cacheMode is the empty string, "local", or "validated".
+
+    // 2. Set entry's initiator type to initiatorType.
+    m_initiator_type = initiator_type;
+
+    // 3. Set entry's requested URL to requestedURL.
+    m_requested_url = requested_url;
+
+    // 4. Set entry's timing info to timingInfo.
+    m_timing_info = timing_info;
+
+    // 5. Set entry's response body info to bodyInfo.
+    m_response_body_info = move(body_info);
+
+    // 6. Set entry's cache mode to cacheMode.
+    m_cache_mode = cache_mode;
+
+    // 7. Set entry's response status to responseStatus.
+    m_response_status = response_status;
+
+    // 8. If deliveryType is the empty string and cacheMode is not, then set deliveryType to "cache".
+    if (delivery_type.is_empty() && cache_mode.has_value())
+        delivery_type = "cache"_fly_string;
+
+    // 9. Set entry's delivery type to deliveryType.
+    m_delivery_type = delivery_type;
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-nexthopprotocol
+FlyString PerformanceResourceTiming::next_hop_protocol() const
+{
+    // The nextHopProtocol getter steps are to isomorphic decode this's timing info's final connection timing info's
+    // ALPN negotiated protocol. See Recording connection timing info for more info.
+    // NOTE: "final connection timing info" can be null, e.g. if this is the timing of a cross-origin resource and
+    //       the Timing-Allow-Origin check fails. We return empty string in this case.
+    if (!m_timing_info->final_connection_timing_info().has_value())
+        return ""_fly_string;
+
+    return m_timing_info->final_connection_timing_info()->alpn_negotiated_protocol;
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-workerstart
+HighResolutionTime::DOMHighResTimeStamp PerformanceResourceTiming::worker_start() const
+{
+    // The workerStart getter steps are to convert fetch timestamp for this's timing info's final service worker start
+    // time and the relevant global object for this. See HTTP fetch for more info.
+    return convert_fetch_timestamp(m_timing_info->final_service_worker_start_time(), HTML::relevant_global_object(*this));
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-redirectstart
+HighResolutionTime::DOMHighResTimeStamp PerformanceResourceTiming::redirect_start() const
+{
+    // The redirectStart getter steps are to convert fetch timestamp for this's timing info's redirect start time and
+    // the relevant global object for this. See HTTP-redirect fetch for more info.
+    return convert_fetch_timestamp(m_timing_info->redirect_start_time(), HTML::relevant_global_object(*this));
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-redirectend
+HighResolutionTime::DOMHighResTimeStamp PerformanceResourceTiming::redirect_end() const
+{
+    // The redirectEnd getter steps are to convert fetch timestamp for this's timing info's redirect end time and the
+    // relevant global object for this. See HTTP-redirect fetch for more info.
+    return convert_fetch_timestamp(m_timing_info->redirect_end_time(), HTML::relevant_global_object(*this));
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-fetchstart
+HighResolutionTime::DOMHighResTimeStamp PerformanceResourceTiming::fetch_start() const
+{
+    // The fetchStart getter steps are to convert fetch timestamp for this's timing info's post-redirect start time and
+    // the relevant global object for this. See HTTP fetch for more info.
+    return convert_fetch_timestamp(m_timing_info->post_redirect_start_time(), HTML::relevant_global_object(*this));
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-domainlookupstart
+HighResolutionTime::DOMHighResTimeStamp PerformanceResourceTiming::domain_lookup_start() const
+{
+    // The domainLookupStart getter steps are to convert fetch timestamp for this's timing info's final connection
+    // timing info's domain lookup start time and the relevant global object for this. See Recording connection timing
+    // info for more info.
+    // NOTE: "final connection timing info" can be null, e.g. if this is the timing of a cross-origin resource and
+    //       the Timing-Allow-Origin check fails. We return 0.0 in this case.
+    if (!m_timing_info->final_connection_timing_info().has_value())
+        return 0.0;
+
+    return convert_fetch_timestamp(m_timing_info->final_connection_timing_info()->domain_lookup_start_time, HTML::relevant_global_object(*this));
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-domainlookupend
+HighResolutionTime::DOMHighResTimeStamp PerformanceResourceTiming::domain_lookup_end() const
+{
+    // The domainLookupEnd getter steps are to convert fetch timestamp for this's timing info's final connection timing
+    // info's domain lookup end time and the relevant global object for this. See Recording connection timing info for
+    // more info.
+    // NOTE: "final connection timing info" can be null, e.g. if this is the timing of a cross-origin resource and
+    //       the Timing-Allow-Origin check fails. We return 0.0 in this case.
+    if (!m_timing_info->final_connection_timing_info().has_value())
+        return 0.0;
+
+    return convert_fetch_timestamp(m_timing_info->final_connection_timing_info()->domain_lookup_end_time, HTML::relevant_global_object(*this));
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-connectstart
+HighResolutionTime::DOMHighResTimeStamp PerformanceResourceTiming::connect_start() const
+{
+    // The connectStart getter steps are to convert fetch timestamp for this's timing info's final connection timing
+    // info's connection start time and the relevant global object for this. See Recording connection timing info for
+    // more info.
+    // NOTE: "final connection timing info" can be null, e.g. if this is the timing of a cross-origin resource and
+    //       the Timing-Allow-Origin check fails. We return 0.0 in this case.
+    if (!m_timing_info->final_connection_timing_info().has_value())
+        return 0.0;
+
+    return convert_fetch_timestamp(m_timing_info->final_connection_timing_info()->connection_start_time, HTML::relevant_global_object(*this));
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-connectend
+HighResolutionTime::DOMHighResTimeStamp PerformanceResourceTiming::connect_end() const
+{
+    // The connectEnd getter steps are to convert fetch timestamp for this's timing info's final connection timing
+    // info's connection end time and the relevant global object for this. See Recording connection timing info for
+    // more info.
+    // NOTE: "final connection timing info" can be null, e.g. if this is the timing of a cross-origin resource and
+    //       the Timing-Allow-Origin check fails. We return 0.0 in this case.
+    if (!m_timing_info->final_connection_timing_info().has_value())
+        return 0.0;
+
+    return convert_fetch_timestamp(m_timing_info->final_connection_timing_info()->connection_end_time, HTML::relevant_global_object(*this));
+}
+
+HighResolutionTime::DOMHighResTimeStamp PerformanceResourceTiming::secure_connection_start() const
+{
+    // The secureConnectionStart getter steps are to convert fetch timestamp for this's timing info's final connection
+    // timing info's secure connection start time and the relevant global object for this. See Recording connection
+    // timing info for more info.
+    // NOTE: "final connection timing info" can be null, e.g. if this is the timing of a cross-origin resource and
+    //       the Timing-Allow-Origin check fails. We return 0.0 in this case.
+    if (!m_timing_info->final_connection_timing_info().has_value())
+        return 0.0;
+
+    return convert_fetch_timestamp(m_timing_info->final_connection_timing_info()->secure_connection_start_time, HTML::relevant_global_object(*this));
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-requeststart
+HighResolutionTime::DOMHighResTimeStamp PerformanceResourceTiming::request_start() const
+{
+    // The requestStart getter steps are to convert fetch timestamp for this's timing info's final network-request
+    // start time and the relevant global object for this. See HTTP fetch for more info.
+    return convert_fetch_timestamp(m_timing_info->final_network_request_start_time(), HTML::relevant_global_object(*this));
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-finalresponseheadersstart
+HighResolutionTime::DOMHighResTimeStamp PerformanceResourceTiming::final_response_headers_start() const
+{
+    // The finalResponseHeadersStart getter steps are to convert fetch timestamp for this's timing info's final
+    // network-response start time and the relevant global object for this. See HTTP fetch for more info.
+    return convert_fetch_timestamp(m_timing_info->final_network_response_start_time(), HTML::relevant_global_object(*this));
+}
+
+HighResolutionTime::DOMHighResTimeStamp PerformanceResourceTiming::first_interim_response_start() const
+{
+    // The firstInterimResponseStart getter steps are to convert fetch timestamp for this's timing info's first interim
+    // network-response start time and the relevant global object for this. See HTTP fetch for more info.
+    return convert_fetch_timestamp(m_timing_info->first_interim_network_response_start_time(), HTML::relevant_global_object(*this));
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-responsestart
+HighResolutionTime::DOMHighResTimeStamp PerformanceResourceTiming::response_start() const
+{
+    // The responseStart getter steps are to return this's firstInterimResponseStart if it is not 0;
+    // Otherwise this's finalResponseHeadersStart.
+    auto first_interim_response_start_time = first_interim_response_start();
+    if (first_interim_response_start_time != 0.0)
+        return first_interim_response_start_time;
+
+    return final_response_headers_start();
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-responseend
+HighResolutionTime::DOMHighResTimeStamp PerformanceResourceTiming::response_end() const
+{
+    // The responseEnd getter steps are to convert fetch timestamp for this's timing info's end time and the relevant
+    // global object for this. See fetch for more info.
+    return convert_fetch_timestamp(m_timing_info->end_time(), HTML::relevant_global_object(*this));
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-encodedbodysize
+u64 PerformanceResourceTiming::encoded_body_size() const
+{
+    // The encodedBodySize getter steps are to return this's resource info's encoded size.
+    return m_response_body_info.encoded_size;
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-decodedbodysize
+u64 PerformanceResourceTiming::decoded_body_size() const
+{
+    // The decodedBodySize getter steps are to return this's resource info's decoded size.
+    return m_response_body_info.decoded_size;
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-transfersize
+u64 PerformanceResourceTiming::transfer_size() const
+{
+    if (m_cache_mode.has_value()) {
+        // 1. If this's cache mode is "local", then return 0.
+        if (m_cache_mode.value() == Fetch::Infrastructure::Response::CacheState::Local)
+            return 0;
+
+        // 2. If this's cache mode is "validated", then return 300.
+        if (m_cache_mode.value() == Fetch::Infrastructure::Response::CacheState::Validated)
+            return 300;
+    }
+
+    // 3. Return this's response body info's encoded size plus 300.
+    // Spec Note: The constant number added to transferSize replaces exposing the total byte size of the HTTP headers,
+    //            as that may expose the presence of certain cookies. See this issue: https://github.com/w3c/resource-timing/issues/238
+    return m_response_body_info.encoded_size + 300;
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-responsestatus
+Fetch::Infrastructure::Status PerformanceResourceTiming::response_status() const
+{
+    // The responseStatus getter steps are to return this's response status.
+    // Spec Note: responseStatus is determined in Fetch. For a cross-origin no-cors request it would be 0 because the
+    // response would be an opaque filtered response.
+    return m_response_status;
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-renderblockingstatus
+Bindings::RenderBlockingStatusType PerformanceResourceTiming::render_blocking_status() const
+{
+    // The renderBlockingStatus getter steps are to return blocking if this's timing info's render-blocking is true;
+    // otherwise non-blocking.
+    if (m_timing_info->render_blocking())
+        return Bindings::RenderBlockingStatusType::Blocking;
+
+    return Bindings::RenderBlockingStatusType::NonBlocking;
+}
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-contenttype
+String const& PerformanceResourceTiming::content_type() const
+{
+    // The contentType getter steps are to return this's resource info's content type.
+    return m_response_body_info.content_type;
+}
+
+}
diff --git a/Libraries/LibWeb/ResourceTiming/PerformanceResourceTiming.h b/Libraries/LibWeb/ResourceTiming/PerformanceResourceTiming.h
new file mode 100644
index 00000000000..7bc6cac944b
--- /dev/null
+++ b/Libraries/LibWeb/ResourceTiming/PerformanceResourceTiming.h
@@ -0,0 +1,90 @@
+/*
+ * Copyright (c) 2025, Luke Wilde <luke@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/FlyString.h>
+#include <LibWeb/Bindings/PerformanceResourceTimingPrototype.h>
+#include <LibWeb/Fetch/Infrastructure/HTTP/Requests.h>
+#include <LibWeb/Fetch/Infrastructure/HTTP/Responses.h>
+#include <LibWeb/PerformanceTimeline/PerformanceEntry.h>
+
+namespace Web::ResourceTiming {
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming
+class PerformanceResourceTiming : public PerformanceTimeline::PerformanceEntry {
+    WEB_PLATFORM_OBJECT(PerformanceResourceTiming, PerformanceTimeline::PerformanceEntry);
+    GC_DECLARE_ALLOCATOR(PerformanceResourceTiming);
+
+public:
+    virtual ~PerformanceResourceTiming() override;
+
+    static void mark_resource_timing(GC::Ref<Fetch::Infrastructure::FetchTimingInfo> timing_info, String const& requested_url, FlyString const& initiator_type, JS::Object& global, Optional<Fetch::Infrastructure::Response::CacheState> const& cache_mode, Fetch::Infrastructure::Response::BodyInfo body_info, Fetch::Infrastructure::Status response_status, FlyString delivery_type = ""_fly_string);
+
+    // NOTE: These three functions are answered by the registry for the given entry type.
+    // https://w3c.github.io/timing-entrytypes-registry/#registry
+
+    // https://w3c.github.io/timing-entrytypes-registry/#dfn-availablefromtimeline
+    static PerformanceTimeline::AvailableFromTimeline available_from_timeline() { return PerformanceTimeline::AvailableFromTimeline::Yes; }
+
+    // https://w3c.github.io/timing-entrytypes-registry/#dfn-maxbuffersize
+    static Optional<u64> max_buffer_size() { return 250; }
+
+    // https://w3c.github.io/timing-entrytypes-registry/#dfn-should-add-entry
+    virtual PerformanceTimeline::ShouldAddEntry should_add_entry(Optional<PerformanceTimeline::PerformanceObserverInit const&> = {}) const override { return PerformanceTimeline::ShouldAddEntry::Yes; }
+
+    virtual FlyString const& entry_type() const override;
+
+    // https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-initiatortype
+    FlyString const& initiator_type() const { return m_initiator_type; }
+
+    // https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-deliverytype
+    FlyString const& delivery_type() const { return m_delivery_type; }
+
+    FlyString next_hop_protocol() const;
+
+    virtual HighResolutionTime::DOMHighResTimeStamp worker_start() const;
+    virtual HighResolutionTime::DOMHighResTimeStamp redirect_start() const;
+    virtual HighResolutionTime::DOMHighResTimeStamp redirect_end() const;
+    virtual HighResolutionTime::DOMHighResTimeStamp fetch_start() const;
+    HighResolutionTime::DOMHighResTimeStamp domain_lookup_start() const;
+    HighResolutionTime::DOMHighResTimeStamp domain_lookup_end() const;
+    HighResolutionTime::DOMHighResTimeStamp connect_start() const;
+    HighResolutionTime::DOMHighResTimeStamp connect_end() const;
+    HighResolutionTime::DOMHighResTimeStamp secure_connection_start() const;
+    HighResolutionTime::DOMHighResTimeStamp request_start() const;
+    HighResolutionTime::DOMHighResTimeStamp final_response_headers_start() const;
+    HighResolutionTime::DOMHighResTimeStamp first_interim_response_start() const;
+    HighResolutionTime::DOMHighResTimeStamp response_start() const;
+    HighResolutionTime::DOMHighResTimeStamp response_end() const;
+    u64 encoded_body_size() const;
+    u64 decoded_body_size() const;
+    u64 transfer_size() const;
+    Fetch::Infrastructure::Status response_status() const;
+    Bindings::RenderBlockingStatusType render_blocking_status() const;
+    String const& content_type() const;
+
+protected:
+    PerformanceResourceTiming(JS::Realm&, String const& name, HighResolutionTime::DOMHighResTimeStamp start_time, HighResolutionTime::DOMHighResTimeStamp duration, GC::Ref<Fetch::Infrastructure::FetchTimingInfo> timing_info);
+
+    void setup_the_resource_timing_entry(FlyString const& initiator_type, String const& requested_url, GC::Ref<Fetch::Infrastructure::FetchTimingInfo> timing_info, Optional<Fetch::Infrastructure::Response::CacheState> const& cache_mode, Fetch::Infrastructure::Response::BodyInfo body_info, Fetch::Infrastructure::Status response_status, FlyString delivery_type = ""_fly_string);
+
+    virtual void initialize(JS::Realm&) override;
+    virtual void visit_edges(JS::Cell::Visitor&) override;
+
+private:
+    FlyString m_initiator_type;
+    String m_requested_url;
+    GC::Ref<Fetch::Infrastructure::FetchTimingInfo> m_timing_info;
+    Fetch::Infrastructure::Response::BodyInfo m_response_body_info;
+    Optional<Fetch::Infrastructure::Response::CacheState> m_cache_mode;
+    Fetch::Infrastructure::Status m_response_status;
+    FlyString m_delivery_type;
+};
+
+HighResolutionTime::DOMHighResTimeStamp convert_fetch_timestamp(HighResolutionTime::DOMHighResTimeStamp time_stamp, JS::Object const& global);
+
+}
diff --git a/Libraries/LibWeb/ResourceTiming/PerformanceResourceTiming.idl b/Libraries/LibWeb/ResourceTiming/PerformanceResourceTiming.idl
new file mode 100644
index 00000000000..dfd62cc49da
--- /dev/null
+++ b/Libraries/LibWeb/ResourceTiming/PerformanceResourceTiming.idl
@@ -0,0 +1,36 @@
+#import <PerformanceTimeline/PerformanceEntry.idl>
+
+// https://w3c.github.io/resource-timing/#dom-renderblockingstatustype
+enum RenderBlockingStatusType {
+    "blocking",
+    "non-blocking"
+};
+
+// https://w3c.github.io/resource-timing/#dom-performanceresourcetiming
+[Exposed=(Window,Worker)]
+interface PerformanceResourceTiming : PerformanceEntry {
+    readonly attribute DOMString initiatorType;
+    readonly attribute DOMString deliveryType;
+    readonly attribute ByteString nextHopProtocol;
+    readonly attribute DOMHighResTimeStamp workerStart;
+    readonly attribute DOMHighResTimeStamp redirectStart;
+    readonly attribute DOMHighResTimeStamp redirectEnd;
+    readonly attribute DOMHighResTimeStamp fetchStart;
+    readonly attribute DOMHighResTimeStamp domainLookupStart;
+    readonly attribute DOMHighResTimeStamp domainLookupEnd;
+    readonly attribute DOMHighResTimeStamp connectStart;
+    readonly attribute DOMHighResTimeStamp connectEnd;
+    readonly attribute DOMHighResTimeStamp secureConnectionStart;
+    readonly attribute DOMHighResTimeStamp requestStart;
+    readonly attribute DOMHighResTimeStamp finalResponseHeadersStart;
+    readonly attribute DOMHighResTimeStamp firstInterimResponseStart;
+    readonly attribute DOMHighResTimeStamp responseStart;
+    readonly attribute DOMHighResTimeStamp responseEnd;
+    readonly attribute unsigned long long  transferSize;
+    readonly attribute unsigned long long  encodedBodySize;
+    readonly attribute unsigned long long  decodedBodySize;
+    readonly attribute unsigned short responseStatus;
+    readonly attribute RenderBlockingStatusType renderBlockingStatus;
+    readonly attribute DOMString contentType;
+    [Default] object toJSON();
+};
diff --git a/Libraries/LibWeb/XHR/XMLHttpRequest.cpp b/Libraries/LibWeb/XHR/XMLHttpRequest.cpp
index 0ac835511a1..fa63675eed4 100644
--- a/Libraries/LibWeb/XHR/XMLHttpRequest.cpp
+++ b/Libraries/LibWeb/XHR/XMLHttpRequest.cpp
@@ -952,8 +952,8 @@ WebIDL::ExceptionOr<void> XMLHttpRequest::send(Optional<DocumentOrXMLHttpRequest
             m_fetch_controller->terminate();
         }
 
-        // FIXME: 7. Report timing for this’s fetch controller given the current global object.
-        //        We cannot do this for responses that have a body yet, as we do not setup the stream that then calls processResponseEndOfBody in `fetch_response_handover`.
+        // 7. Report timing for this’s fetch controller given the current global object.
+        m_fetch_controller->report_timing(HTML::current_principal_global_object());
 
         // 8. Run handle response end-of-body for this.
         TRY(handle_response_end_of_body());
diff --git a/Libraries/LibWeb/idl_files.cmake b/Libraries/LibWeb/idl_files.cmake
index 288dd9b25aa..1ab0f4d7ed2 100644
--- a/Libraries/LibWeb/idl_files.cmake
+++ b/Libraries/LibWeb/idl_files.cmake
@@ -285,6 +285,7 @@ libweb_js_bindings(RequestIdleCallback/IdleDeadline)
 libweb_js_bindings(ResizeObserver/ResizeObserver)
 libweb_js_bindings(ResizeObserver/ResizeObserverEntry)
 libweb_js_bindings(ResizeObserver/ResizeObserverSize)
+libweb_js_bindings(ResourceTiming/PerformanceResourceTiming)
 libweb_js_bindings(ServiceWorker/ServiceWorker)
 libweb_js_bindings(ServiceWorker/ServiceWorkerContainer)
 libweb_js_bindings(ServiceWorker/ServiceWorkerGlobalScope GLOBAL)
diff --git a/Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp b/Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp
index 5bd5b219c89..4fdc25356d7 100644
--- a/Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp
+++ b/Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp
@@ -4523,6 +4523,7 @@ using namespace Web::NavigationTiming;
 using namespace Web::PerformanceTimeline;
 using namespace Web::RequestIdleCallback;
 using namespace Web::ResizeObserver;
+using namespace Web::ResourceTiming;
 using namespace Web::Selection;
 using namespace Web::ServiceWorker;
 using namespace Web::StorageAPI;
diff --git a/Tests/LibWeb/Text/expected/PerformanceObserver/PerformanceObserver-supportedEntryTypes.txt b/Tests/LibWeb/Text/expected/PerformanceObserver/PerformanceObserver-supportedEntryTypes.txt
index 1d7ad1b86a4..f48033b1fe5 100644
--- a/Tests/LibWeb/Text/expected/PerformanceObserver/PerformanceObserver-supportedEntryTypes.txt
+++ b/Tests/LibWeb/Text/expected/PerformanceObserver/PerformanceObserver-supportedEntryTypes.txt
@@ -1,4 +1,4 @@
-PerformanceObserver.supportedEntryTypes: mark,measure
+PerformanceObserver.supportedEntryTypes: mark,measure,resource
 PerformanceObserver.supportedEntryTypes instanceof Array: true
 Object.isFrozen(PerformanceObserver.supportedEntryTypes): true
 PerformanceObserver.supportedEntryTypes === PerformanceObserver.supportedEntryTypes: true
diff --git a/Tests/LibWeb/Text/expected/all-window-properties.txt b/Tests/LibWeb/Text/expected/all-window-properties.txt
index 6f9784f60dc..d15c07921ff 100644
--- a/Tests/LibWeb/Text/expected/all-window-properties.txt
+++ b/Tests/LibWeb/Text/expected/all-window-properties.txt
@@ -282,6 +282,7 @@ PerformanceMeasure
 PerformanceNavigation
 PerformanceObserver
 PerformanceObserverEntryList
+PerformanceResourceTiming
 PerformanceTiming
 PeriodicWave
 Plugin