diff --git a/samples/compound_arguments.cpp b/samples/compound_arguments.cpp
index c44d02d..66d5c92 100644
--- a/samples/compound_arguments.cpp
+++ b/samples/compound_arguments.cpp
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: MIT
+
 #include <argparse/argparse.hpp>
 
 int main(int argc, char *argv[]) {
diff --git a/samples/custom_assignment_characters.cpp b/samples/custom_assignment_characters.cpp
index 7d9ab39..d5deff1 100644
--- a/samples/custom_assignment_characters.cpp
+++ b/samples/custom_assignment_characters.cpp
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: MIT
+
 #include <argparse/argparse.hpp>
 #include <cassert>
 
diff --git a/samples/custom_prefix_characters.cpp b/samples/custom_prefix_characters.cpp
index cdce04d..01e248a 100644
--- a/samples/custom_prefix_characters.cpp
+++ b/samples/custom_prefix_characters.cpp
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: MIT
+
 #include <argparse/argparse.hpp>
 #include <cassert>
 
diff --git a/samples/description_epilog_metavar.cpp b/samples/description_epilog_metavar.cpp
index ef7f11e..02f12dd 100644
--- a/samples/description_epilog_metavar.cpp
+++ b/samples/description_epilog_metavar.cpp
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: MIT
+
 #include <argparse/argparse.hpp>
 
 int main(int argc, char *argv[]) {
diff --git a/samples/gathering_remaining_arguments.cpp b/samples/gathering_remaining_arguments.cpp
index e3fb84e..4f40454 100644
--- a/samples/gathering_remaining_arguments.cpp
+++ b/samples/gathering_remaining_arguments.cpp
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: MIT
+
 #include <argparse/argparse.hpp>
 
 int main(int argc, char *argv[]) {
diff --git a/samples/is_used.cpp b/samples/is_used.cpp
index a2f0a14..27e0373 100644
--- a/samples/is_used.cpp
+++ b/samples/is_used.cpp
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: MIT
+
 #include <argparse/argparse.hpp>
 
 int main(int argc, char *argv[]) {
diff --git a/samples/joining_repeated_optional_arguments.cpp b/samples/joining_repeated_optional_arguments.cpp
index ab819c8..eebbdc6 100644
--- a/samples/joining_repeated_optional_arguments.cpp
+++ b/samples/joining_repeated_optional_arguments.cpp
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: MIT
+
 #include <argparse/argparse.hpp>
 
 int main(int argc, char *argv[]) {
diff --git a/samples/list_of_arguments.cpp b/samples/list_of_arguments.cpp
index ef4d421..e533e47 100644
--- a/samples/list_of_arguments.cpp
+++ b/samples/list_of_arguments.cpp
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: MIT
+
 #include <argparse/argparse.hpp>
 
 int main(int argc, char *argv[]) {
diff --git a/samples/negative_numbers.cpp b/samples/negative_numbers.cpp
index bb1c888..ac4284f 100644
--- a/samples/negative_numbers.cpp
+++ b/samples/negative_numbers.cpp
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: MIT
+
 #include <argparse/argparse.hpp>
 
 int main(int argc, char *argv[]) {
diff --git a/samples/optional_flag_argument.cpp b/samples/optional_flag_argument.cpp
index fff720a..2f85954 100644
--- a/samples/optional_flag_argument.cpp
+++ b/samples/optional_flag_argument.cpp
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: MIT
+
 #include <argparse/argparse.hpp>
 
 int main(int argc, char *argv[]) {
diff --git a/samples/parse_known_args.cpp b/samples/parse_known_args.cpp
index 17b5f4f..e87ead6 100644
--- a/samples/parse_known_args.cpp
+++ b/samples/parse_known_args.cpp
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: MIT
+
 #include <argparse/argparse.hpp>
 #include <cassert>
 
diff --git a/samples/positional_argument.cpp b/samples/positional_argument.cpp
index 646ddc3..03ffb0a 100644
--- a/samples/positional_argument.cpp
+++ b/samples/positional_argument.cpp
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: MIT
+
 #include <argparse/argparse.hpp>
 
 int main(int argc, char *argv[]) {
diff --git a/samples/repeating_argument_to_increase_value.cpp b/samples/repeating_argument_to_increase_value.cpp
index e0de41e..eb1cfd6 100644
--- a/samples/repeating_argument_to_increase_value.cpp
+++ b/samples/repeating_argument_to_increase_value.cpp
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: MIT
+
 #include <argparse/argparse.hpp>
 
 int main(int argc, char *argv[]) {
diff --git a/samples/required_optional_argument.cpp b/samples/required_optional_argument.cpp
index 1fe2dcc..efea523 100644
--- a/samples/required_optional_argument.cpp
+++ b/samples/required_optional_argument.cpp
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: MIT
+
 #include <argparse/argparse.hpp>
 
 int main(int argc, char *argv[]) {
diff --git a/samples/subcommands.cpp b/samples/subcommands.cpp
index f88f05c..74d610e 100644
--- a/samples/subcommands.cpp
+++ b/samples/subcommands.cpp
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: MIT
+
 #include <argparse/argparse.hpp>
 
 int main(int argc, char *argv[]) {