diff --git a/Libraries/LibIPC/AutoCloseFileDescriptor.cpp b/Libraries/LibIPC/AutoCloseFileDescriptor.cpp
new file mode 100644
index 00000000000..95355052d5f
--- /dev/null
+++ b/Libraries/LibIPC/AutoCloseFileDescriptor.cpp
@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2025, the Ladybird developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibCore/System.h>
+#include <LibIPC/AutoCloseFileDescriptor.h>
+
+namespace IPC {
+
+AutoCloseFileDescriptor::AutoCloseFileDescriptor(int fd)
+    : m_fd(fd)
+{
+}
+
+AutoCloseFileDescriptor::~AutoCloseFileDescriptor()
+{
+    if (m_fd != -1)
+        (void)Core::System::close(m_fd);
+}
+
+}
diff --git a/Libraries/LibIPC/AutoCloseFileDescriptor.h b/Libraries/LibIPC/AutoCloseFileDescriptor.h
index 6a2a34820dc..58d39be7e0e 100644
--- a/Libraries/LibIPC/AutoCloseFileDescriptor.h
+++ b/Libraries/LibIPC/AutoCloseFileDescriptor.h
@@ -7,34 +7,19 @@
 #pragma once
 
 #include <AK/RefCounted.h>
-#include <LibCore/System.h>
 
 namespace IPC {
 
 class AutoCloseFileDescriptor : public RefCounted<AutoCloseFileDescriptor> {
 public:
-    AutoCloseFileDescriptor(int fd)
-        : m_fd(fd)
-    {
-    }
-
-    ~AutoCloseFileDescriptor()
-    {
-        if (m_fd != -1)
-            (void)Core::System::close(m_fd);
-    }
+    explicit AutoCloseFileDescriptor(int fd);
+    ~AutoCloseFileDescriptor();
 
     int value() const { return m_fd; }
-
-    int take_fd()
-    {
-        int fd = m_fd;
-        m_fd = -1;
-        return fd;
-    }
+    int take_fd() { return exchange(m_fd, -1); }
 
 private:
-    int m_fd;
+    int m_fd { -1 };
 };
 
 }
diff --git a/Libraries/LibIPC/CMakeLists.txt b/Libraries/LibIPC/CMakeLists.txt
index 74a934e7f62..8d995268941 100644
--- a/Libraries/LibIPC/CMakeLists.txt
+++ b/Libraries/LibIPC/CMakeLists.txt
@@ -1,4 +1,5 @@
 set(SOURCES
+    AutoCloseFileDescriptor.cpp
     Connection.cpp
     Decoder.cpp
     Encoder.cpp
diff --git a/Libraries/LibIPC/File.cpp b/Libraries/LibIPC/File.cpp
index 317b82d05f6..31daa54d00d 100644
--- a/Libraries/LibIPC/File.cpp
+++ b/Libraries/LibIPC/File.cpp
@@ -1,16 +1,65 @@
 /*
  * Copyright (c) 2020, Sergey Bugaev <bugaevc@serenityos.org>
  * Copyright (c) 2021, Andreas Kling <andreas@ladybird.org>
- * Copyright (c) 2023, Tim Flynn <trflynn89@serenityos.org>
+ * Copyright (c) 2023-2025, Tim Flynn <trflynn89@ladybird.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <LibCore/File.h>
+#include <LibCore/System.h>
 #include <LibIPC/Decoder.h>
 #include <LibIPC/File.h>
 
 namespace IPC {
 
+File File::adopt_file(NonnullOwnPtr<Core::File> file)
+{
+    return File(file->leak_fd());
+}
+
+File File::adopt_fd(int fd)
+{
+    return File(fd);
+}
+
+ErrorOr<File> File::clone_fd(int fd)
+{
+    int new_fd = TRY(Core::System::dup(fd));
+    return File(new_fd);
+}
+
+File::File(int fd)
+    : m_fd(fd)
+{
+}
+
+File::File(File&& other)
+    : m_fd(exchange(other.m_fd, -1))
+{
+}
+
+File& File::operator=(File&& other)
+{
+    if (this != &other) {
+        m_fd = exchange(other.m_fd, -1);
+    }
+    return *this;
+}
+
+File::~File()
+{
+    if (m_fd != -1)
+        (void)Core::System::close(m_fd);
+}
+
+// FIXME: IPC::Files transferred over the wire always set O_CLOEXEC during decoding. Perhaps we should add an option to
+//        allow the receiver to decide whether to make it O_CLOEXEC or not. Or an attribute in the .ipc file?
+ErrorOr<void> File::clear_close_on_exec()
+{
+    return Core::System::set_close_on_exec(m_fd, false);
+}
+
 template<>
 ErrorOr<File> decode(Decoder& decoder)
 {
diff --git a/Libraries/LibIPC/File.h b/Libraries/LibIPC/File.h
index c91eeb6a6c0..d0b311a1b65 100644
--- a/Libraries/LibIPC/File.h
+++ b/Libraries/LibIPC/File.h
@@ -9,8 +9,7 @@
 
 #include <AK/Noncopyable.h>
 #include <AK/StdLibExtras.h>
-#include <LibCore/File.h>
-#include <LibCore/System.h>
+#include <LibCore/Forward.h>
 
 namespace IPC {
 
@@ -20,62 +19,24 @@ class File {
 public:
     File() = default;
 
-    static File adopt_file(NonnullOwnPtr<Core::File> file)
-    {
-        return File(file->leak_fd());
-    }
+    static File adopt_file(NonnullOwnPtr<Core::File> file);
+    static File adopt_fd(int fd);
+    static ErrorOr<File> clone_fd(int fd);
 
-    static File adopt_fd(int fd)
-    {
-        return File(fd);
-    }
+    File(File&& other);
+    File& operator=(File&& other);
 
-    static ErrorOr<File> clone_fd(int fd)
-    {
-        int new_fd = TRY(Core::System::dup(fd));
-        return File(new_fd);
-    }
-
-    File(File&& other)
-        : m_fd(exchange(other.m_fd, -1))
-    {
-    }
-
-    File& operator=(File&& other)
-    {
-        if (this != &other) {
-            m_fd = exchange(other.m_fd, -1);
-        }
-        return *this;
-    }
-
-    ~File()
-    {
-        if (m_fd != -1)
-            (void)Core::System::close(m_fd);
-    }
+    ~File();
 
     int fd() const { return m_fd; }
 
-    // NOTE: This is 'const' since generated IPC messages expose all parameters by const reference.
-    [[nodiscard]] int take_fd() const
-    {
-        return exchange(m_fd, -1);
-    }
+    // This is 'const' since generated IPC messages expose all parameters by const reference.
+    [[nodiscard]] int take_fd() const { return exchange(m_fd, -1); }
 
-    // FIXME: IPC::Files transferred over the wire are always set O_CLOEXEC during decoding.
-    //        Perhaps we should add an option to IPC::File to allow the receiver to decide whether to
-    //        make it O_CLOEXEC or not. Or an attribute in the .ipc file?
-    ErrorOr<void> clear_close_on_exec()
-    {
-        return Core::System::set_close_on_exec(m_fd, false);
-    }
+    ErrorOr<void> clear_close_on_exec();
 
 private:
-    explicit File(int fd)
-        : m_fd(fd)
-    {
-    }
+    explicit File(int fd);
 
     mutable int m_fd { -1 };
 };
diff --git a/Libraries/LibIPC/SingleServer.h b/Libraries/LibIPC/SingleServer.h
index a238f00295b..04a2478af6d 100644
--- a/Libraries/LibIPC/SingleServer.h
+++ b/Libraries/LibIPC/SingleServer.h
@@ -6,7 +6,6 @@
 
 #pragma once
 
-#include <LibCore/System.h>
 #include <LibCore/SystemServerTakeover.h>
 #include <LibIPC/ConnectionFromClient.h>
 
diff --git a/Libraries/LibRequests/Request.cpp b/Libraries/LibRequests/Request.cpp
index 73cdb63b32c..15a0d2d3e41 100644
--- a/Libraries/LibRequests/Request.cpp
+++ b/Libraries/LibRequests/Request.cpp
@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <LibCore/File.h>
 #include <LibRequests/Request.h>
 #include <LibRequests/RequestClient.h>
 
diff --git a/Libraries/LibWeb/CMakeLists.txt b/Libraries/LibWeb/CMakeLists.txt
index 0293ce17406..b635a4b1429 100644
--- a/Libraries/LibWeb/CMakeLists.txt
+++ b/Libraries/LibWeb/CMakeLists.txt
@@ -592,6 +592,8 @@ set(SOURCES
     HTML/NavigationTransition.cpp
     HTML/Navigator.cpp
     HTML/NavigatorBeacon.cpp
+    HTML/NavigatorConcurrentHardware.cpp
+    HTML/NavigatorDeviceMemory.cpp
     HTML/NavigatorID.cpp
     HTML/Numbers.cpp
     HTML/OffscreenCanvas.cpp
diff --git a/Libraries/LibWeb/HTML/NavigatorConcurrentHardware.cpp b/Libraries/LibWeb/HTML/NavigatorConcurrentHardware.cpp
new file mode 100644
index 00000000000..c5ccee160cb
--- /dev/null
+++ b/Libraries/LibWeb/HTML/NavigatorConcurrentHardware.cpp
@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2022, Andrew Kaster <akaster@serenityos.org>
+ * Copyright (c) 2024, Shannon Booth <shannon@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibCore/System.h>
+#include <LibWeb/HTML/NavigatorConcurrentHardware.h>
+
+namespace Web::HTML {
+
+// https://html.spec.whatwg.org/multipage/workers.html#dom-navigator-hardwareconcurrency
+WebIDL::UnsignedLongLong NavigatorConcurrentHardwareMixin::hardware_concurrency()
+{
+    return Core::System::hardware_concurrency();
+}
+
+}
diff --git a/Libraries/LibWeb/HTML/NavigatorConcurrentHardware.h b/Libraries/LibWeb/HTML/NavigatorConcurrentHardware.h
index ff0c303159b..bc5144e4c20 100644
--- a/Libraries/LibWeb/HTML/NavigatorConcurrentHardware.h
+++ b/Libraries/LibWeb/HTML/NavigatorConcurrentHardware.h
@@ -7,15 +7,13 @@
 
 #pragma once
 
-#include <LibCore/System.h>
 #include <LibWeb/WebIDL/Types.h>
 
 namespace Web::HTML {
 
 class NavigatorConcurrentHardwareMixin {
 public:
-    // https://html.spec.whatwg.org/multipage/workers.html#dom-navigator-hardwareconcurrency
-    static WebIDL::UnsignedLongLong hardware_concurrency() { return Core::System::hardware_concurrency(); }
+    static WebIDL::UnsignedLongLong hardware_concurrency();
 };
 
 }
diff --git a/Libraries/LibWeb/HTML/NavigatorDeviceMemory.cpp b/Libraries/LibWeb/HTML/NavigatorDeviceMemory.cpp
new file mode 100644
index 00000000000..7e1ec77b5ac
--- /dev/null
+++ b/Libraries/LibWeb/HTML/NavigatorDeviceMemory.cpp
@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2024, Jelle Raaijmakers <jelle@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/BuiltinWrappers.h>
+#include <LibCore/System.h>
+#include <LibWeb/HTML/NavigatorDeviceMemory.h>
+
+namespace Web::HTML {
+
+// https://www.w3.org/TR/device-memory/#computing-device-memory-value
+WebIDL::Double NavigatorDeviceMemoryMixin::device_memory() const
+{
+    // The value is calculated by using the actual device memory in MiB then rounding it to the nearest number where
+    // only the most significant bit can be set and the rest are zeros (nearest power of two).
+    auto memory_in_bytes = Core::System::physical_memory_bytes();
+    auto memory_in_mib = memory_in_bytes / MiB;
+    auto required_bits = AK::count_required_bits(memory_in_mib);
+    auto lower_memory_in_mib = static_cast<u64>(1) << (required_bits - 1);
+    auto upper_memory_in_mib = static_cast<u64>(1) << required_bits;
+    auto rounded_memory_in_mib = upper_memory_in_mib - memory_in_mib <= memory_in_mib - lower_memory_in_mib
+        ? upper_memory_in_mib
+        : lower_memory_in_mib;
+
+    // Then dividing that number by 1024.0 to get the value in GiB.
+    auto memory_in_gib = static_cast<WebIDL::Double>(rounded_memory_in_mib) / 1024.0;
+
+    // An upper bound and a lower bound should be set on the list of values.
+    return AK::clamp(memory_in_gib, 1.0, 4.0);
+}
+
+}
diff --git a/Libraries/LibWeb/HTML/NavigatorDeviceMemory.h b/Libraries/LibWeb/HTML/NavigatorDeviceMemory.h
index 83eca4e041e..52fbbe51e46 100644
--- a/Libraries/LibWeb/HTML/NavigatorDeviceMemory.h
+++ b/Libraries/LibWeb/HTML/NavigatorDeviceMemory.h
@@ -6,35 +6,13 @@
 
 #pragma once
 
-#include <AK/BuiltinWrappers.h>
-#include <LibCore/System.h>
 #include <LibWeb/WebIDL/Types.h>
 
 namespace Web::HTML {
 
 class NavigatorDeviceMemoryMixin {
 public:
-    // https://www.w3.org/TR/device-memory/#computing-device-memory-value
-    WebIDL::Double device_memory() const
-    {
-        // The value is calculated by using the actual device memory in MiB then rounding it to the
-        // nearest number where only the most significant bit can be set and the rest are zeros
-        // (nearest power of two).
-        auto memory_in_bytes = Core::System::physical_memory_bytes();
-        auto memory_in_mib = memory_in_bytes / MiB;
-        auto required_bits = AK::count_required_bits(memory_in_mib);
-        auto lower_memory_in_mib = static_cast<u64>(1) << (required_bits - 1);
-        auto upper_memory_in_mib = static_cast<u64>(1) << required_bits;
-        auto rounded_memory_in_mib = upper_memory_in_mib - memory_in_mib <= memory_in_mib - lower_memory_in_mib
-            ? upper_memory_in_mib
-            : lower_memory_in_mib;
-
-        // Then dividing that number by 1024.0 to get the value in GiB.
-        auto memory_in_gib = static_cast<WebIDL::Double>(rounded_memory_in_mib) / 1024.0;
-
-        // An upper bound and a lower bound should be set on the list of values.
-        return AK::clamp(memory_in_gib, 1.0, 4.0);
-    }
+    WebIDL::Double device_memory() const;
 };
 
 }
diff --git a/Libraries/LibWeb/Loader/ResourceLoader.cpp b/Libraries/LibWeb/Loader/ResourceLoader.cpp
index cb31a9922c0..42cf2f9bea6 100644
--- a/Libraries/LibWeb/Loader/ResourceLoader.cpp
+++ b/Libraries/LibWeb/Loader/ResourceLoader.cpp
@@ -9,6 +9,7 @@
 #include <LibCore/Directory.h>
 #include <LibCore/MimeData.h>
 #include <LibCore/Resource.h>
+#include <LibCore/System.h>
 #include <LibGC/Function.h>
 #include <LibRequests/Request.h>
 #include <LibRequests/RequestClient.h>
diff --git a/Libraries/LibWebView/HelperProcess.cpp b/Libraries/LibWebView/HelperProcess.cpp
index 2481db46514..50658cde2fd 100644
--- a/Libraries/LibWebView/HelperProcess.cpp
+++ b/Libraries/LibWebView/HelperProcess.cpp
@@ -6,6 +6,7 @@
 
 #include <AK/Enumerate.h>
 #include <LibCore/Process.h>
+#include <LibCore/System.h>
 #include <LibWebView/Application.h>
 #include <LibWebView/HelperProcess.h>
 #include <LibWebView/Utilities.h>
diff --git a/Libraries/LibWebView/Process.cpp b/Libraries/LibWebView/Process.cpp
index 9759ec1d325..aaa83c312e3 100644
--- a/Libraries/LibWebView/Process.cpp
+++ b/Libraries/LibWebView/Process.cpp
@@ -8,7 +8,9 @@
 #include <LibCore/Process.h>
 #include <LibCore/Socket.h>
 #include <LibCore/StandardPaths.h>
+#include <LibCore/System.h>
 #include <LibWebView/Process.h>
+
 #if defined(AK_OS_WINDOWS)
 #    include <AK/ScopeGuard.h>
 #    include <AK/Windows.h>
diff --git a/Services/ImageDecoder/ConnectionFromClient.cpp b/Services/ImageDecoder/ConnectionFromClient.cpp
index ed5d1f65f24..dbaf1a769e3 100644
--- a/Services/ImageDecoder/ConnectionFromClient.cpp
+++ b/Services/ImageDecoder/ConnectionFromClient.cpp
@@ -8,6 +8,7 @@
 #include <AK/IDAllocator.h>
 #include <ImageDecoder/ConnectionFromClient.h>
 #include <ImageDecoder/ImageDecoderClientEndpoint.h>
+#include <LibCore/System.h>
 #include <LibGfx/Bitmap.h>
 #include <LibGfx/ImageFormats/ImageDecoder.h>
 #include <LibGfx/ImageFormats/TIFFMetadata.h>
diff --git a/Services/RequestServer/ConnectionFromClient.cpp b/Services/RequestServer/ConnectionFromClient.cpp
index 52b2cf523ed..f816fb14758 100644
--- a/Services/RequestServer/ConnectionFromClient.cpp
+++ b/Services/RequestServer/ConnectionFromClient.cpp
@@ -10,6 +10,7 @@
 #include <LibCore/Proxy.h>
 #include <LibCore/Socket.h>
 #include <LibCore/StandardPaths.h>
+#include <LibCore/System.h>
 #include <LibHTTP/Cache/DiskCache.h>
 #include <LibRequests/WebSocket.h>
 #include <LibWebSocket/ConnectionInfo.h>
diff --git a/Tests/LibWeb/test-web/Fixture.cpp b/Tests/LibWeb/test-web/Fixture.cpp
index 599619ed43f..b39dc188aed 100644
--- a/Tests/LibWeb/test-web/Fixture.cpp
+++ b/Tests/LibWeb/test-web/Fixture.cpp
@@ -11,6 +11,7 @@
 #include <AK/LexicalPath.h>
 #include <LibCore/Process.h>
 #include <LibCore/StandardPaths.h>
+#include <LibCore/System.h>
 
 namespace TestWeb {
 
diff --git a/Tests/LibWeb/test-web/main.cpp b/Tests/LibWeb/test-web/main.cpp
index 25102e24770..9bf9e8f94ba 100644
--- a/Tests/LibWeb/test-web/main.cpp
+++ b/Tests/LibWeb/test-web/main.cpp
@@ -23,6 +23,7 @@
 #include <LibCore/Directory.h>
 #include <LibCore/EventLoop.h>
 #include <LibCore/File.h>
+#include <LibCore/System.h>
 #include <LibCore/Timer.h>
 #include <LibDiff/Format.h>
 #include <LibDiff/Generator.h>