diff --git a/dspace_statistics_api/app.py b/dspace_statistics_api/app.py
index 736eed1..9ada088 100644
--- a/dspace_statistics_api/app.py
+++ b/dspace_statistics_api/app.py
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: GPL-3.0-only
+
 import json
 import math
 
diff --git a/dspace_statistics_api/config.py b/dspace_statistics_api/config.py
index e5d8937..2f1eed0 100644
--- a/dspace_statistics_api/config.py
+++ b/dspace_statistics_api/config.py
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: GPL-3.0-only
+
 import os
 
 # Check if Solr connection information was provided in the environment
diff --git a/dspace_statistics_api/database.py b/dspace_statistics_api/database.py
index ab991a9..94f7a7c 100644
--- a/dspace_statistics_api/database.py
+++ b/dspace_statistics_api/database.py
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: GPL-3.0-only
+
 import falcon
 import psycopg2
 import psycopg2.extras
diff --git a/dspace_statistics_api/indexer.py b/dspace_statistics_api/indexer.py
index 77f9352..99d8072 100644
--- a/dspace_statistics_api/indexer.py
+++ b/dspace_statistics_api/indexer.py
@@ -1,23 +1,7 @@
+# SPDX-License-Identifier: GPL-3.0-only
 #
 # indexer.py
 #
-# Copyright 2018 Alan Orth.
-#
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# ---
-#
 # Connects to a DSpace Solr statistics core and ingests views and downloads for
 # communities, collections, and items into a PostgreSQL database.
 #
diff --git a/dspace_statistics_api/stats.py b/dspace_statistics_api/stats.py
index b56320e..a7abafb 100644
--- a/dspace_statistics_api/stats.py
+++ b/dspace_statistics_api/stats.py
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: GPL-3.0-only
+
 import requests
 
 from .config import SOLR_SERVER
diff --git a/dspace_statistics_api/util.py b/dspace_statistics_api/util.py
index 3078d41..8fd1203 100644
--- a/dspace_statistics_api/util.py
+++ b/dspace_statistics_api/util.py
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: GPL-3.0-only
+
 import datetime
 import json
 import re
diff --git a/tests/test_api_collections.py b/tests/test_api_collections.py
index 6b8b82e..bd487d2 100644
--- a/tests/test_api_collections.py
+++ b/tests/test_api_collections.py
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: GPL-3.0-only
+
 import json
 from unittest.mock import patch
 
diff --git a/tests/test_api_communities.py b/tests/test_api_communities.py
index 418c010..56b6d80 100644
--- a/tests/test_api_communities.py
+++ b/tests/test_api_communities.py
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: GPL-3.0-only
+
 import json
 from unittest.mock import patch
 
diff --git a/tests/test_api_docs.py b/tests/test_api_docs.py
index 3dfa626..6525222 100644
--- a/tests/test_api_docs.py
+++ b/tests/test_api_docs.py
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: GPL-3.0-only
+
 import pytest
 from falcon import testing
 
diff --git a/tests/test_api_items.py b/tests/test_api_items.py
index dd52c7a..08bad96 100644
--- a/tests/test_api_items.py
+++ b/tests/test_api_items.py
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: GPL-3.0-only
+
 import json
 from unittest.mock import patch