diff --git a/AK/String.cpp b/AK/String.cpp
index 34608280232..8286084063f 100644
--- a/AK/String.cpp
+++ b/AK/String.cpp
@@ -11,6 +11,7 @@
 #include <AK/MemMem.h>
 #include <AK/Stream.h>
 #include <AK/String.h>
+#include <AK/StringInternals.h>
 #include <AK/Vector.h>
 #include <stdlib.h>
 
@@ -18,69 +19,6 @@ namespace AK {
 
 namespace Detail {
 
-class StringData final : public RefCounted<StringData> {
-public:
-    static ErrorOr<NonnullRefPtr<StringData>> create_uninitialized(size_t, u8*& buffer);
-    static ErrorOr<NonnullRefPtr<StringData>> create_substring(StringData const& superstring, size_t start, size_t byte_count);
-    static ErrorOr<NonnullRefPtr<StringData>> from_utf8(char const* utf8_bytes, size_t);
-    static ErrorOr<NonnullRefPtr<StringData>> from_stream(Stream&, size_t byte_count);
-
-    struct SubstringData {
-        StringData const* superstring { nullptr };
-        u32 start_offset { 0 };
-    };
-
-    void operator delete(void* ptr);
-
-    ~StringData();
-
-    SubstringData const& substring_data() const
-    {
-        return *reinterpret_cast<SubstringData const*>(m_bytes_or_substring_data);
-    }
-
-    // NOTE: There is no guarantee about null-termination.
-    ReadonlyBytes bytes() const
-    {
-        if (m_substring) {
-            auto const& data = substring_data();
-            return data.superstring->bytes().slice(data.start_offset, m_byte_count);
-        }
-        return { &m_bytes_or_substring_data[0], m_byte_count };
-    }
-
-    StringView bytes_as_string_view() const { return { bytes() }; }
-
-    bool operator==(StringData const& other) const
-    {
-        return bytes_as_string_view() == other.bytes_as_string_view();
-    }
-
-    unsigned hash() const
-    {
-        if (!m_has_hash)
-            compute_hash();
-        return m_hash;
-    }
-
-    bool is_fly_string() const { return m_is_fly_string; }
-    void set_fly_string(bool is_fly_string) const { m_is_fly_string = is_fly_string; }
-
-private:
-    explicit StringData(size_t byte_count);
-    StringData(StringData const& superstring, size_t start, size_t byte_count);
-
-    void compute_hash() const;
-
-    u32 m_byte_count { 0 };
-    mutable unsigned m_hash { 0 };
-    mutable bool m_has_hash { false };
-    bool m_substring { false };
-    mutable bool m_is_fly_string { false };
-
-    alignas(SubstringData) u8 m_bytes_or_substring_data[0];
-};
-
 void StringData::operator delete(void* ptr)
 {
     free(ptr);
diff --git a/AK/StringInternals.h b/AK/StringInternals.h
new file mode 100644
index 00000000000..64a06f18864
--- /dev/null
+++ b/AK/StringInternals.h
@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2023, Dan Klishch <danilklishch@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/NonnullRefPtr.h>
+#include <AK/RefCounted.h>
+#include <AK/Span.h>
+#include <AK/StringView.h>
+
+namespace AK::Detail {
+
+class StringData final : public RefCounted<StringData> {
+public:
+    static ErrorOr<NonnullRefPtr<StringData>> create_uninitialized(size_t, u8*& buffer);
+    static ErrorOr<NonnullRefPtr<StringData>> create_substring(StringData const& superstring, size_t start, size_t byte_count);
+    static ErrorOr<NonnullRefPtr<StringData>> from_utf8(char const* utf8_bytes, size_t);
+    static ErrorOr<NonnullRefPtr<StringData>> from_stream(Stream&, size_t byte_count);
+
+    struct SubstringData {
+        StringData const* superstring { nullptr };
+        u32 start_offset { 0 };
+    };
+
+    void operator delete(void* ptr);
+
+    ~StringData();
+
+    SubstringData const& substring_data() const
+    {
+        return *reinterpret_cast<SubstringData const*>(m_bytes_or_substring_data);
+    }
+
+    // NOTE: There is no guarantee about null-termination.
+    ReadonlyBytes bytes() const
+    {
+        if (m_substring) {
+            auto const& data = substring_data();
+            return data.superstring->bytes().slice(data.start_offset, m_byte_count);
+        }
+        return { &m_bytes_or_substring_data[0], m_byte_count };
+    }
+
+    StringView bytes_as_string_view() const { return { bytes() }; }
+
+    bool operator==(StringData const& other) const
+    {
+        return bytes_as_string_view() == other.bytes_as_string_view();
+    }
+
+    unsigned hash() const
+    {
+        if (!m_has_hash)
+            compute_hash();
+        return m_hash;
+    }
+
+    bool is_fly_string() const { return m_is_fly_string; }
+    void set_fly_string(bool is_fly_string) const { m_is_fly_string = is_fly_string; }
+
+private:
+    explicit StringData(size_t byte_count);
+    StringData(StringData const& superstring, size_t start, size_t byte_count);
+
+    void compute_hash() const;
+
+    u32 m_byte_count { 0 };
+    mutable unsigned m_hash { 0 };
+    mutable bool m_has_hash { false };
+    bool m_substring { false };
+    mutable bool m_is_fly_string { false };
+
+    alignas(SubstringData) u8 m_bytes_or_substring_data[0];
+};
+
+}