diff --git a/CMakeLists.txt b/CMakeLists.txt
index b130e10d..9a0475d3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -21,6 +21,9 @@ INCLUDE(GNUInstallDirs)
 
 LIST( APPEND CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake )
 
+# Load C++20 module support
+INCLUDE( SIOModules )
+
 # options
 OPTION( SIO_EXAMPLES                 "Switch ON to build SIO examples" ON )
 OPTION( INSTALL_DOC                  "Set to OFF to skip build/install Documentation" OFF )
@@ -38,6 +41,16 @@ ENDIF()
 # ZLIB package
 IF( SIO_BUILTIN_ZLIB )
   ADD_SUBDIRECTORY( zlib )
+  # Install ZLIB when SIO modules are enabled (needed for export)
+  # Note: This makes ZLIB visible to downstream users as SIO::ZLIB when modules are enabled.
+  #       This is required by CMake's export mechanism for targets with FILE_SET CXX_MODULES.
+  #       The ZLIB target is static and should not conflict with system ZLIB libraries.
+  IF( SIO_ENABLE_CXX_MODULES )
+    INSTALL( TARGETS ZLIB
+      EXPORT SIOTargets
+      ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
+    )
+  ENDIF()
 ELSE()
   FIND_PACKAGE( ZLIB REQUIRED )
 ENDIF()
diff --git a/cmake/SIOModules.cmake b/cmake/SIOModules.cmake
new file mode 100644
index 00000000..01cf44cf
--- /dev/null
+++ b/cmake/SIOModules.cmake
@@ -0,0 +1,84 @@
+#---------------------------------------------------------------------------------------------------
+# CMake support for C++20 modules in SIO
+#
+# This file provides macros and options for generating and using C++20 module interfaces
+# for the SIO library.
+#---------------------------------------------------------------------------------------------------
+
+# Option to enable C++20 module generation
+option(SIO_ENABLE_CXX_MODULES "Generate C++20 module interface files (.ixx) for SIO" OFF)
+
+# Check if modules are actually supported
+if(SIO_ENABLE_CXX_MODULES)
+  # Check CMake version
+  if(CMAKE_VERSION VERSION_LESS 3.29)
+    message(WARNING "C++20 modules require CMake 3.29 or later (found ${CMAKE_VERSION}). Disabling module support.")
+    set(SIO_ENABLE_CXX_MODULES OFF CACHE BOOL "C++20 modules disabled due to CMake version" FORCE)
+  endif()
+
+  # Check generator
+  if(CMAKE_GENERATOR STREQUAL "Unix Makefiles")
+    message(WARNING "C++20 modules are not supported with the Unix Makefiles generator. Please use Ninja. Disabling module support.")
+    set(SIO_ENABLE_CXX_MODULES OFF CACHE BOOL "C++20 modules disabled due to generator" FORCE)
+  endif()
+
+  # Check compiler support
+  if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+    if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 14.0)
+      message(WARNING "C++20 modules require GCC 14 or later (found ${CMAKE_CXX_COMPILER_VERSION}). Disabling module support.")
+      set(SIO_ENABLE_CXX_MODULES OFF CACHE BOOL "C++20 modules disabled due to compiler version" FORCE)
+    endif()
+  elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 18.0)
+      message(WARNING "C++20 modules require Clang 18 or later (found ${CMAKE_CXX_COMPILER_VERSION}). Disabling module support.")
+      set(SIO_ENABLE_CXX_MODULES OFF CACHE BOOL "C++20 modules disabled due to compiler version" FORCE)
+    endif()
+  else()
+    message(WARNING "C++20 modules have only been tested with GCC 14+ and Clang 18+. Found ${CMAKE_CXX_COMPILER_ID}. Proceed at your own risk.")
+  endif()
+endif()
+
+if(SIO_ENABLE_CXX_MODULES)
+  message(STATUS "C++20 module support is ENABLED for SIO")
+else()
+  message(STATUS "C++20 module support is DISABLED for SIO")
+endif()
+
+#---------------------------------------------------------------------------------------------------
+# SIO_ADD_MODULE_INTERFACE( target module_file )
+#
+# Add a C++20 module interface to a SIO target.
+#
+# This function conditionally adds a module interface file to the specified target when
+# SIO_ENABLE_CXX_MODULES is ON. The module interface is added as a PUBLIC CXX_MODULES file set,
+# which makes it available for installation and use by downstream projects.
+#
+# When SIO_ENABLE_CXX_MODULES is OFF, this function returns immediately without any action.
+#
+# Arguments:
+#   target      - The target to which the module interface should be added
+#   module_file - The .ixx file implementing the module interface (absolute or relative path)
+#
+# Example:
+#   SIO_ADD_MODULE_INTERFACE(sio ${CMAKE_CURRENT_SOURCE_DIR}/sio_module.ixx)
+#
+# Note:
+#   The module_file should be installed separately using INSTALL(TARGETS ... FILE_SET CXX_MODULES)
+#   when SIO_ENABLE_CXX_MODULES is ON.
+#---------------------------------------------------------------------------------------------------
+function(SIO_ADD_MODULE_INTERFACE target module_file)
+  if(NOT SIO_ENABLE_CXX_MODULES)
+    return()
+  endif()
+
+  message(STATUS "Adding C++20 module 'sio' to target '${target}'")
+
+  # Add the module file to the target as a CXX_MODULES file set
+  # Use PUBLIC so the module gets installed and can be used by downstream projects
+  target_sources(${target}
+    PUBLIC
+      FILE_SET CXX_MODULES
+      BASE_DIRS ${CMAKE_CURRENT_SOURCE_DIR}
+      FILES ${module_file}
+  )
+endfunction()
diff --git a/source/CMakeLists.txt b/source/CMakeLists.txt
index 4333e448..202975cd 100644
--- a/source/CMakeLists.txt
+++ b/source/CMakeLists.txt
@@ -26,9 +26,25 @@ IF( SIO_MACROS_WITH_EXCEPTION )
   TARGET_COMPILE_DEFINITIONS(sio PUBLIC "-DSIO_MACROS_WITH_EXCEPTION=1")
 ENDIF()
 
-SIO_INSTALL_SHARED_LIBRARY( sio
-  EXPORT SIOTargets
-  DESTINATION ${CMAKE_INSTALL_LIBDIR} )
+# Add C++20 module interface if enabled (before install)
+IF( SIO_ENABLE_CXX_MODULES )
+  SIO_ADD_MODULE_INTERFACE( sio ${CMAKE_CURRENT_SOURCE_DIR}/sio_module.ixx )
+  # Install library with module file set
+  INSTALL( TARGETS sio
+    EXPORT SIOTargets
+    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
+    FILE_SET CXX_MODULES DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/sio/modules
+    PERMISSIONS
+      OWNER_READ OWNER_WRITE OWNER_EXECUTE
+      GROUP_READ GROUP_EXECUTE
+      WORLD_READ WORLD_EXECUTE
+  )
+ELSE()
+  # Install library without modules
+  SIO_INSTALL_SHARED_LIBRARY( sio
+    EXPORT SIOTargets
+    DESTINATION ${CMAKE_INSTALL_LIBDIR} )
+ENDIF()
 
 # install SIO headers
 SIO_INSTALL_DIRECTORY( include/sio DESTINATION ${CMAKE_INSTALL_INCLUDEDIR} )
diff --git a/source/include/sio/definitions.h b/source/include/sio/definitions.h
index b2921445..c3b285cb 100644
--- a/source/include/sio/definitions.h
+++ b/source/include/sio/definitions.h
@@ -108,35 +108,35 @@ namespace sio {
   using block_list = std::vector<block_ptr> ;
 
   /// The null byte definition
-  static constexpr byte null_byte = '\0' ;
+  inline constexpr byte null_byte = '\0' ;
   
-  static constexpr byte padding_bytes [4] = {null_byte} ;
+  inline constexpr byte padding_bytes [4] = {null_byte} ;
   /// Kilo byte unit
-  static constexpr std::size_t kbyte = 0x00000400 ;
+  inline constexpr std::size_t kbyte = 0x00000400 ;
   /// Mega byte unit
-  static constexpr std::size_t mbyte = 0x00100000 ;
+  inline constexpr std::size_t mbyte = 0x00100000 ;
   /// The compression bit mask
-  static constexpr unsigned int compression_bit = 0x00000001 ;
+  inline constexpr unsigned int compression_bit = 0x00000001 ;
   /// The bit alignment mask
-  static constexpr unsigned int bit_align = 0x00000003 ;
+  inline constexpr unsigned int bit_align = 0x00000003 ;
   /// The additional padding added in buffer IO
-  static constexpr unsigned int padding = 3 ;
+  inline constexpr unsigned int padding = 3 ;
   /// The additional padding mask
-  static constexpr unsigned int padding_mask = 0xfffffffc ;
+  inline constexpr unsigned int padding_mask = 0xfffffffc ;
   /// The record marker
-  static constexpr unsigned int record_marker = 0xabadcafe ;
+  inline constexpr unsigned int record_marker = 0xabadcafe ;
   /// The block marker
-  static constexpr unsigned int block_marker  = 0xdeadbeef ;
+  inline constexpr unsigned int block_marker  = 0xdeadbeef ;
   /// The maximum length of a record name
-  static constexpr std::size_t max_record_name_len = 64 ;
+  inline constexpr std::size_t max_record_name_len = 64 ;
   /// The maximum length of a record_info in memory
-  static constexpr std::size_t max_record_info_len = 2*sizeof(sio::ifstream::pos_type) + 5*sizeof(unsigned int) + max_record_name_len ;
+  inline constexpr std::size_t max_record_info_len = 2*sizeof(sio::ifstream::pos_type) + 5*sizeof(unsigned int) + max_record_name_len ;
 
   // TODO: Do we still need all of this ??
-  static constexpr std::size_t single_len = 1 ;
-  static constexpr std::size_t double_len = 2 ;
-  static constexpr std::size_t quad_len = 4 ;
-  static constexpr std::size_t octo_len = 8 ;
+  inline constexpr std::size_t single_len = 1 ;
+  inline constexpr std::size_t double_len = 2 ;
+  inline constexpr std::size_t quad_len = 4 ;
+  inline constexpr std::size_t octo_len = 8 ;
 
   /**
    *  @brief  record_info struct.
diff --git a/source/include/sio/memcpy.h b/source/include/sio/memcpy.h
index 93bf79cd..ab03f832 100644
--- a/source/include/sio/memcpy.h
+++ b/source/include/sio/memcpy.h
@@ -16,13 +16,13 @@ namespace sio {
    */
   template <typename T>
   struct sizeof_helper {
-    static constexpr std::size_t size = sizeof(T) ;
+    static inline constexpr std::size_t size = sizeof(T) ;
   };
 
 #define SIO_FORCE_SIZEOF( TYPE, SIZE ) \
   template <> \
   struct sizeof_helper<TYPE> { \
-    static constexpr std::size_t size = SIZE ; \
+    static inline constexpr std::size_t size = SIZE ; \
   }
 
   SIO_FORCE_SIZEOF( char, 1 ) ;
diff --git a/source/sio_module.ixx b/source/sio_module.ixx
new file mode 100644
index 00000000..948634b7
--- /dev/null
+++ b/source/sio_module.ixx
@@ -0,0 +1,109 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Module interface for SIO - Simple I/O library
+//
+// This module exports the core SIO types and interfaces.
+
+module;
+
+// Global module fragment - includes go here
+#include <cctype>
+#include <cstdint>
+#include <fstream>
+#include <functional>
+#include <iostream>
+#include <map>
+#include <memory>
+#include <string>
+#include <type_traits>
+#include <vector>
+
+#ifdef __APPLE__
+#include <_types.h>
+#include <_types/_uint16_t.h>
+#include <_types/_uint32_t.h>
+#include <_types/_uint64_t.h>
+#include <_types/_uint8_t.h>
+#include <sys/_types/_int16_t.h>
+#include <sys/_types/_int64_t.h>
+#else
+#include <stdint.h>
+#endif
+
+// SIO headers
+#include "sio/definitions.h"
+#include "sio/exception.h"
+#include "sio/version.h"
+#include "sio/buffer.h"
+#include "sio/block.h"
+#include "sio/io_device.h"
+#include "sio/memcpy.h"
+#include "sio/api.h"
+#include "sio/compression/zlib.h"
+
+export module sio;
+
+// Export SIO namespace and types
+export namespace sio {
+  // Type aliases from definitions.h
+  using sio::byte;
+  using sio::byte_array;
+  using sio::byte_traits;
+  using sio::index_type;
+  using sio::options_type;
+  using sio::version_type;
+  using sio::ptr_type;
+  using sio::pointed_at_map;
+  using sio::pointer_to_map;
+  using sio::ifstream;
+  using sio::ofstream;
+  using sio::fstream;
+  using sio::block_ptr;
+  using sio::block_list;
+
+  // Constants from definitions.h
+  using sio::null_byte;
+  using sio::padding_bytes;
+  using sio::kbyte;
+  using sio::mbyte;
+  using sio::compression_bit;
+  using sio::bit_align;
+  using sio::padding;
+  using sio::padding_mask;
+  using sio::record_marker;
+  using sio::block_marker;
+  using sio::max_record_name_len;
+  using sio::max_record_info_len;
+  using sio::single_len;
+  using sio::double_len;
+  using sio::quad_len;
+  using sio::octo_len;
+
+  // Structs and enums from definitions.h
+  using sio::record_info;
+  using sio::validate;
+  using sio::valid_record_name;
+
+  // Exception types
+  using sio::exception;
+  using sio::error_code;
+
+  // Version class
+  using sio::version;
+
+  // Core classes
+  using sio::buffer;
+  using sio::buffer_span;
+  using sio::block;
+  using sio::read_device;
+  using sio::write_device;
+
+  // Memory copy utilities
+  using sio::memcpy;
+  using sio::sizeof_helper;
+
+  // API class and functions
+  using sio::api;
+
+  // Compression
+  using sio::zlib_compression;
+}