diff --git a/ci/manifest.sh b/ci/manifest.sh
index 1a126afb..bb3e3c98 100755
--- a/ci/manifest.sh
+++ b/ci/manifest.sh
@@ -1,4 +1,5 @@
 #!/usr/bin/env bash
+# SPDX-License-Identifier: Apache-2.0 OR MIT
 set -euxo pipefail
 IFS=$'\n\t'
 cd "$(dirname "$0")"/..
diff --git a/main.sh b/main.sh
index 2bec4df8..6fdfa86a 100755
--- a/main.sh
+++ b/main.sh
@@ -1,4 +1,5 @@
 #!/usr/bin/env bash
+# SPDX-License-Identifier: Apache-2.0 OR MIT
 set -euo pipefail
 IFS=$'\n\t'
 
diff --git a/tools/.tidy-check-license-headers b/tools/.tidy-check-license-headers
new file mode 100644
index 00000000..3c5d9a0c
--- /dev/null
+++ b/tools/.tidy-check-license-headers
@@ -0,0 +1 @@
+git ls-files '*.sh' # TODO: check more files
diff --git a/tools/manifest.sh b/tools/manifest.sh
index ad40ddda..9fd588f4 100755
--- a/tools/manifest.sh
+++ b/tools/manifest.sh
@@ -1,4 +1,5 @@
 #!/usr/bin/env bash
+# SPDX-License-Identifier: Apache-2.0 OR MIT
 set -euo pipefail
 IFS=$'\n\t'
 cd "$(dirname "$0")"/..
diff --git a/tools/publish.sh b/tools/publish.sh
index 502c3d9f..af738151 100755
--- a/tools/publish.sh
+++ b/tools/publish.sh
@@ -1,4 +1,5 @@
 #!/usr/bin/env bash
+# SPDX-License-Identifier: Apache-2.0 OR MIT
 set -euo pipefail
 IFS=$'\n\t'
 cd "$(dirname "$0")"/..
diff --git a/tools/tidy.sh b/tools/tidy.sh
index 1f2fda37..d48866ca 100755
--- a/tools/tidy.sh
+++ b/tools/tidy.sh
@@ -201,6 +201,44 @@ else
     warn "'shellcheck' is not installed"
 fi
 
+# License check
+# TODO: This check is still experimental and does not track all files that should be tracked.
+if [[ -f tools/.tidy-check-license-headers ]]; then
+    info "checking license headers (experimental)"
+    failed_files=''
+    for p in $(eval $(<tools/.tidy-check-license-headers)); do
+        # TODO: More file types?
+        case "$(basename "${p}")" in
+            *.sh) prefix=("# ") ;;
+            *.rs | *.c | *.h | *.cpp | *.hpp | *.s | *.S) prefix=("// " "/* ") ;;
+            *.ld | *.x) prefix=("/* ") ;;
+            *) error "unrecognized file type: ${p}" ;;
+        esac
+        # TODO: The exact line number is not actually important; it is important
+        # that it be part of the top-level comments of the file.
+        line="1"
+        case "${p}" in
+            *.sh) line="2" ;; # shebang
+        esac
+        header_found=''
+        for pre in "${prefix[@]}"; do
+            if [[ "$(grep -E -n "${pre}SPDX-License-Identifier: " "${p}")" == "${line}:${pre}SPDX-License-Identifier: "* ]]; then
+                header_found='1'
+                continue
+            fi
+        done
+        if [[ -z "${header_found}" ]]; then
+            failed_files+="${p}:${line}"$'\n'
+        fi
+    done
+    if [[ -n "${failed_files}" ]]; then
+        error "license-check failed: please add SPDX-License-Identifier to the following files"
+        echo "======================================="
+        echo -n "${failed_files}"
+        echo "======================================="
+    fi
+fi
+
 # Spell check (if config exists)
 if [[ -f .cspell.json ]]; then
     info "spell checking"