diff --git a/.LICENSE b/.LICENSE
new file mode 100644
index 0000000..15867e3
--- /dev/null
+++ b/.LICENSE
@@ -0,0 +1,6 @@
+Khaos
+C/C++ library for writing cross-platform codes.
+
+SPDX-FileCopyrightText: 2019-2024 flagarde
+
+SPDX-License-Identifier: MIT
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 740cfff..727804d 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -50,6 +50,9 @@ repos:
   - id: remove-tabs
     name: tabs remover
     args: [--whitespaces-count, '2']
+  - id: insert-license
+    files: \.(h(pp)|h(pp.in)|c(pp)|h.in|c?)$
+    args: [--license-filepath, .LICENSE, --comment-style, /*|*|*/, --use-current-year, --fuzzy-match-generates-todo, --fuzzy-ratio-cut-off, '85', --fuzzy-match-todo-instructions, ' TODO: Delete the inconsistent license and above line and rerun pre-commit to insert a good license. If this is the desired behavior add "//  insert-license=off" at the beginning to the file.', --skip-license-insertion-comment, '//  insert-license=off' ]
 
 - repo: https://github.com/codespell-project/codespell
   rev: v2.2.2
diff --git a/include/khaos/C.h b/include/khaos/C.h
index d88e15a..6d561e6 100644
--- a/include/khaos/C.h
+++ b/include/khaos/C.h
@@ -1,8 +1,16 @@
+/*
+* Khaos
+* C/C++ library for writing cross-platform codes.
+*
+* SPDX-FileCopyrightText: 2020-2024 flagarde
+*
+* SPDX-License-Identifier: MIT
+*/
+
 #ifndef KHAOS_C_H_
 #define KHAOS_C_H_
 
 /** \file C.h
- *  \copyright 2022 flagarde
  *  \brief Detect the C standard and define some useful macros.
  */
 
diff --git a/include/khaos/CStandards.h b/include/khaos/CStandards.h
index afff84b..d71e21d 100644
--- a/include/khaos/CStandards.h
+++ b/include/khaos/CStandards.h
@@ -1,8 +1,16 @@
+/*
+* Khaos
+* C/C++ library for writing cross-platform codes.
+*
+* SPDX-FileCopyrightText: 2020-2024 flagarde
+*
+* SPDX-License-Identifier: MIT
+*/
+
 #ifndef KHAOS_CSTANDARDS_H_
 #define KHAOS_CSTANDARDS_H_
 
 /*! \file CStandards.h
- *  \copyright 2022 flagarde
  *  \brief Define the values of the official C standard.
  *   Define macros that expand to the integer constant of type \b long whose value are the version of the C standard.
  *   Official values for the \b __STDC_VERSION__ macro.
@@ -13,5 +21,6 @@
 #define KHAOS_STANDARD_C99_PRIVATE() (199901L) /*!< Value for the C99 standard */
 #define KHAOS_STANDARD_C11_PRIVATE() (201112L) /*!< Value for the C11 standard */
 #define KHAOS_STANDARD_C17_PRIVATE() (201710L) /*!< Value for the C17 standard */
+#define KHAOS_STANDARD_C23_PRIVATE() (202311L) /*!< Value for the C23 standard */
 
 #endif /* KHAOS_CSTANDARDS_H_ */
diff --git a/include/khaos/CXX.h b/include/khaos/CXX.h
index 892e447..93482ec 100644
--- a/include/khaos/CXX.h
+++ b/include/khaos/CXX.h
@@ -1,8 +1,16 @@
+/*
+* Khaos
+* C/C++ library for writing cross-platform codes.
+*
+* SPDX-FileCopyrightText: 2020-2024 flagarde
+*
+* SPDX-License-Identifier: MIT
+*/
+
 #ifndef KHAOS_CXX_H_
 #define KHAOS_CXX_H_
 
 /*! \file CXX.h
- *  \copyright 2022 flagarde
  *  \brief Detect the C++ standard and define some useful macros.
  *  \warning \b CXX11 is always false for \b MSVC only c++14 and upper are considered.
 */
diff --git a/include/khaos/CXXStandards.h b/include/khaos/CXXStandards.h
index e80b048..5c79d55 100644
--- a/include/khaos/CXXStandards.h
+++ b/include/khaos/CXXStandards.h
@@ -1,8 +1,16 @@
+/*
+* Khaos
+* C/C++ library for writing cross-platform codes.
+*
+* SPDX-FileCopyrightText: 2020-2024 flagarde
+*
+* SPDX-License-Identifier: MIT
+*/
+
 #ifndef KHAOS_CXXSTANDARDS_H_
 #define KHAOS_CXXSTANDARDS_H_
 
 /*! \file CXXStandards.h
- *  \copyright 2022 flagarde
  *  \brief Define the version of the C++ standard.
  *  Define macros that expand to the integer constant of type \b long whose value are the version of the C++ standard.
  *  Official values for the \b __cplusplus macro.
@@ -13,5 +21,6 @@
 #define KHAOS_STANDARD_CXX14_PRIVATE() (201402L) /*!< Value for the C++14 standard */
 #define KHAOS_STANDARD_CXX17_PRIVATE() (201703L) /*!< Value for the C++17 standard */
 #define KHAOS_STANDARD_CXX20_PRIVATE() (202002L) /*!< Value for the C++20 standard */
+#define KHAOS_STANDARD_CXX23_PRIVATE() (202302L) /*!< Value for the C++23 standard */
 
 #endif /* KHAOS_CXXSTANDARDS_H_ */
diff --git a/include/khaos/CompareVersionMacros.h b/include/khaos/CompareVersionMacros.h
index b5c6540..d05e57c 100644
--- a/include/khaos/CompareVersionMacros.h
+++ b/include/khaos/CompareVersionMacros.h
@@ -1,3 +1,12 @@
+/*
+* Khaos
+* C/C++ library for writing cross-platform codes.
+*
+* SPDX-FileCopyrightText: 2020-2024 flagarde
+*
+* SPDX-License-Identifier: MIT
+*/
+
 #ifndef KHAOS_COMPAREVERSIONMACROS_H_
 #define KHAOS_COMPAREVERSIONMACROS_H_
 
@@ -5,7 +14,6 @@
 #include "khaos/VersionMacros.h"
 
 /** \file CompareVersionMacros.h
- *  \copyright 2022 flagarde
  *  \brief Define macros to compare versions.
  *  \note Use these macros only if you need preprocessor version checking.
  *  \note For example :
diff --git a/include/khaos/KhaosVersion.h.in b/include/khaos/KhaosVersion.h.in
index d06b583..1c17c9e 100644
--- a/include/khaos/KhaosVersion.h.in
+++ b/include/khaos/KhaosVersion.h.in
@@ -1,5 +1,13 @@
+/*
+* Khaos
+* C/C++ library for writing cross-platform codes.
+*
+* SPDX-FileCopyrightText: 2020-2024 flagarde
+*
+* SPDX-License-Identifier: MIT
+*/
+
 /** \file KhaosVersion.h
- *  \copyright 2022 flagarde
  *
  *  \brief Macros providing the Khaos version.
  *
diff --git a/include/khaos/Language.h b/include/khaos/Language.h
index a30412b..33f045c 100644
--- a/include/khaos/Language.h
+++ b/include/khaos/Language.h
@@ -1,8 +1,16 @@
+/*
+* Khaos
+* C/C++ library for writing cross-platform codes.
+*
+* SPDX-FileCopyrightText: 2020-2024 flagarde
+*
+* SPDX-License-Identifier: MIT
+*/
+
 #ifndef KHAOS_LANGUAGE_H_
 #define KHAOS_LANGUAGE_H_
 
 /*! \file Languages.h
- *  \copyright 2022 flagarde
  *  \brief Detect the languages and define some useful macros.
 */
 
diff --git a/include/khaos/VersionMacros.h b/include/khaos/VersionMacros.h
index e29b50d..9142029 100644
--- a/include/khaos/VersionMacros.h
+++ b/include/khaos/VersionMacros.h
@@ -1,8 +1,16 @@
+/*
+* Khaos
+* C/C++ library for writing cross-platform codes.
+*
+* SPDX-FileCopyrightText: 2020-2024 flagarde
+*
+* SPDX-License-Identifier: MIT
+*/
+
 #ifndef KHAOS_VERSIONMACROS_H_
 #define KHAOS_VERSIONMACROS_H_
 
 /** \file VersionMacros.h
- *  \copyright 2022 flagarde
  *  \brief Define macros to set, get versions.
  *  \note Use these macros only if you need preprocessor version checking.
  *  \note For example :
diff --git a/tests/CStandards.test.cpp b/tests/CStandards.test.cpp
index 6931119..2b7bf80 100644
--- a/tests/CStandards.test.cpp
+++ b/tests/CStandards.test.cpp
@@ -1,3 +1,12 @@
+/*
+* Khaos
+* C/C++ library for writing cross-platform codes.
+*
+* SPDX-FileCopyrightText: 2020-2024 flagarde
+*
+* SPDX-License-Identifier: MIT
+*/
+
 /* Copyright 2022 flagarde */
 
 #define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
diff --git a/tests/CXXStandards.test.cpp b/tests/CXXStandards.test.cpp
index 09fc8aa..a976824 100644
--- a/tests/CXXStandards.test.cpp
+++ b/tests/CXXStandards.test.cpp
@@ -1,3 +1,12 @@
+/*
+* Khaos
+* C/C++ library for writing cross-platform codes.
+*
+* SPDX-FileCopyrightText: 2020-2024 flagarde
+*
+* SPDX-License-Identifier: MIT
+*/
+
 /* Copyright 2022 flagarde */
 
 #define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
diff --git a/tests/CompareVersionMacros.test.cpp b/tests/CompareVersionMacros.test.cpp
index 905828e..2586015 100644
--- a/tests/CompareVersionMacros.test.cpp
+++ b/tests/CompareVersionMacros.test.cpp
@@ -1,3 +1,12 @@
+/*
+* Khaos
+* C/C++ library for writing cross-platform codes.
+*
+* SPDX-FileCopyrightText: 2020-2024 flagarde
+*
+* SPDX-License-Identifier: MIT
+*/
+
 /* Copyright 2022 flagarde */
 
 #include "khaos/CompareVersionMacros.h"
diff --git a/tests/KhaosVersion.test.cpp b/tests/KhaosVersion.test.cpp
index 0f88b73..f433811 100644
--- a/tests/KhaosVersion.test.cpp
+++ b/tests/KhaosVersion.test.cpp
@@ -1,3 +1,12 @@
+/*
+* Khaos
+* C/C++ library for writing cross-platform codes.
+*
+* SPDX-FileCopyrightText: 2020-2024 flagarde
+*
+* SPDX-License-Identifier: MIT
+*/
+
 /* Copyright 2022 flagarde */
 #include "khaos/KhaosVersion.h"
 
diff --git a/tests/LanguageC.test.c b/tests/LanguageC.test.c
index 0441d6b..77fbd92 100644
--- a/tests/LanguageC.test.c
+++ b/tests/LanguageC.test.c
@@ -1,3 +1,12 @@
+/*
+* Khaos
+* C/C++ library for writing cross-platform codes.
+*
+* SPDX-FileCopyrightText: 2024-2024 flagarde
+*
+* SPDX-License-Identifier: MIT
+*/
+
 /* Copyright 2022 flagarde */
 
 #include "khaos/Language.h"
diff --git a/tests/LanguageCXX.test.cpp b/tests/LanguageCXX.test.cpp
index 9c370b3..d41fb63 100644
--- a/tests/LanguageCXX.test.cpp
+++ b/tests/LanguageCXX.test.cpp
@@ -1,3 +1,12 @@
+/*
+* Khaos
+* C/C++ library for writing cross-platform codes.
+*
+* SPDX-FileCopyrightText: 2020-2024 flagarde
+*
+* SPDX-License-Identifier: MIT
+*/
+
 /* Copyright 2022 flagarde */
 /* doctest need c++11 so disable it to test C++98 */
 
diff --git a/tests/VersionMacros.test.cpp b/tests/VersionMacros.test.cpp
index 0293463..3691860 100644
--- a/tests/VersionMacros.test.cpp
+++ b/tests/VersionMacros.test.cpp
@@ -1,3 +1,12 @@
+/*
+* Khaos
+* C/C++ library for writing cross-platform codes.
+*
+* SPDX-FileCopyrightText: 2020-2024 flagarde
+*
+* SPDX-License-Identifier: MIT
+*/
+
 /* Copyright 2022 flagarde */
 
 #include "khaos/VersionMacros.h"