diff --git a/.eslintrc.json b/.eslintrc.json
index 297f7500..4bed4a0d 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -14,7 +14,10 @@
         "es2017": true,
         "webextensions": true
     },
-    "plugins": ["no-unsanitized"],
+    "plugins": [
+        "no-unsanitized",
+        "header"
+    ],
     "ignorePatterns": [
         "/ext/lib/"
     ],
@@ -82,7 +85,26 @@
         "template-tag-spacing": ["error", "never"],
 
         "no-unsanitized/method": "error",
-        "no-unsanitized/property": "error"
+        "no-unsanitized/property": "error",
+
+        "header/header": ["error", "block", [
+            "",
+            {"pattern": " \\* Copyright \\(C\\) (\\d+-)?2021  Yomichan Authors"},
+            " *",
+            " * 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 <https://www.gnu.org/licenses/>.",
+            " "
+        ]]
     },
     "overrides": [
         {
diff --git a/ext/js/display/display-generator.js b/ext/js/display/display-generator.js
index da1b053a..b904c16e 100644
--- a/ext/js/display/display-generator.js
+++ b/ext/js/display/display-generator.js
@@ -12,7 +12,7 @@
  * 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/>.
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
 /* global
diff --git a/ext/js/dom/html-template-collection.js b/ext/js/dom/html-template-collection.js
index 52d5f3b0..271986cb 100644
--- a/ext/js/dom/html-template-collection.js
+++ b/ext/js/dom/html-template-collection.js
@@ -12,7 +12,7 @@
  * 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/>.
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
 class HtmlTemplateCollection {
diff --git a/ext/js/input/hotkey-help-controller.js b/ext/js/input/hotkey-help-controller.js
index 9bf95c77..3f33a1f4 100644
--- a/ext/js/input/hotkey-help-controller.js
+++ b/ext/js/input/hotkey-help-controller.js
@@ -12,7 +12,7 @@
  * 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/>.
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
 /* global
diff --git a/ext/js/input/hotkey-util.js b/ext/js/input/hotkey-util.js
index ea3daf97..3e6d6388 100644
--- a/ext/js/input/hotkey-util.js
+++ b/ext/js/input/hotkey-util.js
@@ -12,7 +12,7 @@
  * 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/>.
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
 /**
diff --git a/ext/js/pages/settings/backup-controller.js b/ext/js/pages/settings/backup-controller.js
index 649645d4..6f6614b6 100644
--- a/ext/js/pages/settings/backup-controller.js
+++ b/ext/js/pages/settings/backup-controller.js
@@ -8,7 +8,7 @@
  *
  * 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.  the
+ * 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
diff --git a/package-lock.json b/package-lock.json
index 586a71c3..10983b5a 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -3310,6 +3310,12 @@
                 "v8-compile-cache": "^2.0.3"
             }
         },
+        "eslint-plugin-header": {
+            "version": "3.1.1",
+            "resolved": "https://registry.npmjs.org/eslint-plugin-header/-/eslint-plugin-header-3.1.1.tgz",
+            "integrity": "sha512-9vlKxuJ4qf793CmeeSrZUvVClw6amtpghq3CuWcB5cUNnWHQhgcqy5eF8oVKFk1G3Y/CbchGfEaw3wiIJaNmVg==",
+            "dev": true
+        },
         "eslint-plugin-no-unsanitized": {
             "version": "3.1.4",
             "resolved": "https://registry.npmjs.org/eslint-plugin-no-unsanitized/-/eslint-plugin-no-unsanitized-3.1.4.tgz",
diff --git a/package.json b/package.json
index 5453926d..4ef284e8 100644
--- a/package.json
+++ b/package.json
@@ -37,6 +37,7 @@
     "devDependencies": {
         "browserify": "^16.5.2",
         "eslint": "^7.15.0",
+        "eslint-plugin-header": "^3.1.1",
         "eslint-plugin-no-unsanitized": "^3.1.4",
         "fake-indexeddb": "^3.1.2",
         "html-validate": "^4.3.0",
diff --git a/test/data/html/test-document2-script.js b/test/data/html/test-document2-script.js
index 01bc211f..8e381b09 100644
--- a/test/data/html/test-document2-script.js
+++ b/test/data/html/test-document2-script.js
@@ -1,3 +1,20 @@
+/*
+ * Copyright (C) 2021  Yomichan Authors
+ *
+ * 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 <https://www.gnu.org/licenses/>.
+ */
+
 function requestFullscreen(element) {
     if (element.requestFullscreen) {
         element.requestFullscreen();