diff --git a/src/basic/MurmurHash2.c b/src/basic/MurmurHash2.c
index 5859af0a81..43a89a0820 100644
--- a/src/basic/MurmurHash2.c
+++ b/src/basic/MurmurHash2.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: LicenseRef-murmurhash2-public-domain */
 //-----------------------------------------------------------------------------
 // MurmurHash2 was written by Austin Appleby, and is placed in the public
 // domain. The author hereby disclaims copyright to this source code.
diff --git a/src/basic/MurmurHash2.h b/src/basic/MurmurHash2.h
index 1aef3afba0..5758b86039 100644
--- a/src/basic/MurmurHash2.h
+++ b/src/basic/MurmurHash2.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: LicenseRef-murmurhash2-public-domain */
 //-----------------------------------------------------------------------------
 // MurmurHash2 was written by Austin Appleby, and is placed in the public
 // domain. The author hereby disclaims copyright to this source code.
diff --git a/src/basic/gunicode.c b/src/basic/gunicode.c
index c51b1a7a18..02637d74e9 100644
--- a/src/basic/gunicode.c
+++ b/src/basic/gunicode.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
 /* gunicode.c - Unicode manipulation functions
  *
  *  Copyright (C) 1999, 2000 Tom Tromey
diff --git a/src/basic/gunicode.h b/src/basic/gunicode.h
index a16b7b6ff1..765077db83 100644
--- a/src/basic/gunicode.h
+++ b/src/basic/gunicode.h
@@ -1,10 +1,10 @@
-#pragma once
-
+/* SPDX-License-Identifier: LGPL-2.1+ */
 /* gunicode.h - Unicode manipulation functions
  *
  *  Copyright (C) 1999, 2000 Tom Tromey
  *  Copyright © 2000, 2005 Red Hat, Inc.
  */
+#pragma once
 
 #include <stdbool.h>
 #include <stdint.h>
diff --git a/src/basic/memory-util.c b/src/basic/memory-util.c
index 5f327ef0d7..0a5cf2797d 100644
--- a/src/basic/memory-util.c
+++ b/src/basic/memory-util.c
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 #include <unistd.h>
 
 #include "memory-util.h"
diff --git a/src/basic/siphash24.c b/src/basic/siphash24.c
index 61180819b1..7c61eb145d 100644
--- a/src/basic/siphash24.c
+++ b/src/basic/siphash24.c
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: CC0-1.0 */
+
 /*
    SipHash reference C implementation
 
@@ -10,7 +12,7 @@
    worldwide. This software is distributed without any warranty.
 
    You should have received a copy of the CC0 Public Domain Dedication along with
-   this software. If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
+   this software. If not, see <https://creativecommons.org/publicdomain/zero/1.0/>.
 
    (Minimal changes made by Lennart Poettering, to make clean for inclusion in systemd)
    (Refactored by Tom Gundersen to split up in several functions and follow systemd
diff --git a/src/basic/siphash24.h b/src/basic/siphash24.h
index fe43256882..90a6de00e4 100644
--- a/src/basic/siphash24.h
+++ b/src/basic/siphash24.h
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: CC0-1.0 */
+
 #pragma once
 
 #include <inttypes.h>
diff --git a/src/basic/sort-util.c b/src/basic/sort-util.c
index 5cf0d1d49b..77342c4bdc 100644
--- a/src/basic/sort-util.c
+++ b/src/basic/sort-util.c
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 #include "sort-util.h"
 #include "alloc-util.h"
 
diff --git a/src/basic/static-destruct.h b/src/basic/static-destruct.h
index 8fbc07c587..fbb8fa087b 100644
--- a/src/basic/static-destruct.h
+++ b/src/basic/static-destruct.h
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 #pragma once
 
 #include "alloc-util.h"
diff --git a/src/boot/efi/crc32.c b/src/boot/efi/crc32.c
index 46b9aeea90..5dfd3db265 100644
--- a/src/boot/efi/crc32.c
+++ b/src/boot/efi/crc32.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: LicenseRef-crc32-no-restriction */
 /* This is copied from util-linux, which in turn copied in the version from Gary S. Brown */
 
 /*
diff --git a/src/boot/efi/crc32.h b/src/boot/efi/crc32.h
index 64150ee948..3af543b84e 100644
--- a/src/boot/efi/crc32.h
+++ b/src/boot/efi/crc32.h
@@ -1,4 +1,4 @@
-/* SPDX-License-Identifier: LGPL-2.1+ */
+/* SPDX-License-Identifier: LicenseRef-crc32-no-restriction */
 #pragma once
 
 #include <efi.h>
diff --git a/src/boot/efi/random-seed.c b/src/boot/efi/random-seed.c
index cc747993b8..6e2a6f1d32 100644
--- a/src/boot/efi/random-seed.c
+++ b/src/boot/efi/random-seed.c
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 #include <efi.h>
 #include <efilib.h>
 
diff --git a/src/boot/efi/sha256.c b/src/boot/efi/sha256.c
index 40da636dc7..005e1902d4 100644
--- a/src/boot/efi/sha256.c
+++ b/src/boot/efi/sha256.c
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 /* Stolen from glibc and converted to UEFI style. In glibc it comes with the following copyright blurb: */
 
 /* Functions to compute SHA256 message digest of files or memory blocks.
diff --git a/src/home/user-record-sign.c b/src/home/user-record-sign.c
index 91f8639997..6ef0c27c54 100644
--- a/src/home/user-record-sign.c
+++ b/src/home/user-record-sign.c
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 #include <openssl/pem.h>
 
 #include "fd-util.h"
diff --git a/src/journal-remote/journal-upload.h b/src/journal-remote/journal-upload.h
index 4994cd8391..95af35db05 100644
--- a/src/journal-remote/journal-upload.h
+++ b/src/journal-remote/journal-upload.h
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 #pragma once
 
 #include <inttypes.h>
diff --git a/src/journal/lookup3.c b/src/journal/lookup3.c
index 74c80b724d..39967f21cd 100644
--- a/src/journal/lookup3.c
+++ b/src/journal/lookup3.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: LicenseRef-lookup3-public-domain */
 /* Slightly modified by Lennart Poettering, to avoid name clashes, and
  * unexport a few functions. */
 
diff --git a/src/journal/lookup3.h b/src/journal/lookup3.h
index 0a01269e43..04e493e95e 100644
--- a/src/journal/lookup3.h
+++ b/src/journal/lookup3.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: LicenseRef-lookup3-public-domain */
 #pragma once
 
 #include <inttypes.h>
diff --git a/src/libsystemd-network/test-sd-dhcp-lease.c b/src/libsystemd-network/test-sd-dhcp-lease.c
index 534cc78564..91eaf814e4 100644
--- a/src/libsystemd-network/test-sd-dhcp-lease.c
+++ b/src/libsystemd-network/test-sd-dhcp-lease.c
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 #include <errno.h>
 
 #include "dhcp-lease-internal.h"
diff --git a/src/libsystemd/sd-bus/test-bus-address.c b/src/libsystemd/sd-bus/test-bus-address.c
index 70a6df10f9..1316d376e1 100644
--- a/src/libsystemd/sd-bus/test-bus-address.c
+++ b/src/libsystemd/sd-bus/test-bus-address.c
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 #include "sd-bus.h"
 
 #include "bus-internal.h"
diff --git a/src/network/netdev/wireguard.h b/src/network/netdev/wireguard.h
index 61113113e4..e2c06f0377 100644
--- a/src/network/netdev/wireguard.h
+++ b/src/network/netdev/wireguard.h
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 #pragma once
 
 typedef struct Wireguard Wireguard;
diff --git a/src/network/test-network-tables.c b/src/network/test-network-tables.c
index 25b9396397..7743c63d4a 100644
--- a/src/network/test-network-tables.c
+++ b/src/network/test-network-tables.c
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 #include "bond.h"
 #include "dhcp6-internal.h"
 #include "dhcp6-protocol.h"
diff --git a/src/resolve/resolved-dnssd-bus.h b/src/resolve/resolved-dnssd-bus.h
index 403455e89f..e51c9ac145 100644
--- a/src/resolve/resolved-dnssd-bus.h
+++ b/src/resolve/resolved-dnssd-bus.h
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 #pragma once
 
 #include "sd-bus.h"
diff --git a/src/resolve/resolved-dnssd.h b/src/resolve/resolved-dnssd.h
index 304bd890c9..faba11ca53 100644
--- a/src/resolve/resolved-dnssd.h
+++ b/src/resolve/resolved-dnssd.h
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 #pragma once
 
 #include "list.h"
diff --git a/src/shared/binfmt-util.c b/src/shared/binfmt-util.c
index 0229726b42..c673c0435d 100644
--- a/src/shared/binfmt-util.c
+++ b/src/shared/binfmt-util.c
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 #include <sys/stat.h>
 #include <sys/statvfs.h>
 #include <sys/vfs.h>
diff --git a/src/shared/dm-util.c b/src/shared/dm-util.c
index 7efcb6b2aa..cfb13bad4c 100644
--- a/src/shared/dm-util.c
+++ b/src/shared/dm-util.c
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 #include <fcntl.h>
 #include <linux/dm-ioctl.h>
 #include <sys/ioctl.h>
diff --git a/src/shared/initreq.h b/src/shared/initreq.h
index 1d7ff81df1..1bf5b8edd7 100644
--- a/src/shared/initreq.h
+++ b/src/shared/initreq.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: LGPL-2+ */
 /*
  * initreq.h	Interface to talk to init through /dev/initctl.
  *
diff --git a/src/shared/linux/nl80211.h b/src/shared/linux/nl80211.h
index b065c1fe4d..65edfff1ca 100644
--- a/src/shared/linux/nl80211.h
+++ b/src/shared/linux/nl80211.h
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: MIT */
+
 #ifndef __LINUX_NL80211_H
 #define __LINUX_NL80211_H
 /*
diff --git a/src/shared/pam-util.c b/src/shared/pam-util.c
index f000798ce0..ff44df7762 100644
--- a/src/shared/pam-util.c
+++ b/src/shared/pam-util.c
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 #include <security/pam_ext.h>
 #include <syslog.h>
 #include <stdlib.h>
diff --git a/src/shared/pe-header.h b/src/shared/pe-header.h
index a362917523..13cb1d8a15 100644
--- a/src/shared/pe-header.h
+++ b/src/shared/pe-header.h
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 #pragma once
 
 #include <inttypes.h>
diff --git a/src/shared/qrcode-util.c b/src/shared/qrcode-util.c
index 4094c4ff3b..96d3df493a 100644
--- a/src/shared/qrcode-util.c
+++ b/src/shared/qrcode-util.c
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 #include "qrcode-util.h"
 
 #if HAVE_QRENCODE
diff --git a/src/test/test-sd-hwdb.c b/src/test/test-sd-hwdb.c
index eb34d8eab2..8746a841d4 100644
--- a/src/test/test-sd-hwdb.c
+++ b/src/test/test-sd-hwdb.c
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
 #include "sd-hwdb.h"
 
 #include "alloc-util.h"
diff --git a/src/time-wait-sync/time-wait-sync.c b/src/time-wait-sync/time-wait-sync.c
index 96072445f6..02053e7708 100644
--- a/src/time-wait-sync/time-wait-sync.c
+++ b/src/time-wait-sync/time-wait-sync.c
@@ -1,11 +1,5 @@
-/*
- * systemd service to wait until kernel realtime clock is synchronized
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
- * USA
- */
+/* SPDX-License-Identifier: LGPL-2.1+ */
+/* systemd service to wait until kernel realtime clock is synchronized */
 
 #include <errno.h>
 #include <stdbool.h>