diff --git a/package-lock.json b/package-lock.json
index 4a5e9a3c..dcffc9a3 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -5046,12 +5046,14 @@
         "balanced-match": {
           "version": "1.0.0",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "brace-expansion": {
           "version": "1.1.11",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "balanced-match": "^1.0.0",
             "concat-map": "0.0.1"
@@ -5066,17 +5068,20 @@
         "code-point-at": {
           "version": "1.1.0",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "concat-map": {
           "version": "0.0.1",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "console-control-strings": {
           "version": "1.1.0",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "core-util-is": {
           "version": "1.0.2",
@@ -5193,7 +5198,8 @@
         "inherits": {
           "version": "2.0.3",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "ini": {
           "version": "1.3.5",
@@ -5205,6 +5211,7 @@
           "version": "1.0.0",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "number-is-nan": "^1.0.0"
           }
@@ -5219,6 +5226,7 @@
           "version": "3.0.4",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "brace-expansion": "^1.1.7"
           }
@@ -5226,12 +5234,14 @@
         "minimist": {
           "version": "0.0.8",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "minipass": {
           "version": "2.2.4",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "safe-buffer": "^5.1.1",
             "yallist": "^3.0.0"
@@ -5250,6 +5260,7 @@
           "version": "0.5.1",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "minimist": "0.0.8"
           }
@@ -5330,7 +5341,8 @@
         "number-is-nan": {
           "version": "1.0.1",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "object-assign": {
           "version": "4.1.1",
@@ -5342,6 +5354,7 @@
           "version": "1.4.0",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "wrappy": "1"
           }
@@ -5463,6 +5476,7 @@
           "version": "1.0.2",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "code-point-at": "^1.0.0",
             "is-fullwidth-code-point": "^1.0.0",
diff --git a/src/excmds.ts b/src/excmds.ts
index ee26ad81..736f8bef 100644
--- a/src/excmds.ts
+++ b/src/excmds.ts
@@ -1923,11 +1923,29 @@ export async function reader() {
 loadaucmds("DocStart")
 window.addEventListener("pagehide", () => loadaucmds("DocEnd"))
 window.addEventListener("DOMContentLoaded", () => loadaucmds("DocLoad"))
+/** @hidden */
+const fullscreenhandler = () => {
+    loadaucmds("FullscreenChange")
+    if (document.fullscreenElement || (document as any).mozFullScreenElement) {
+        loadaucmds("FullscreenEnter")
+    } else {
+        loadaucmds("FullscreenLeft")
+    }
+}
+
+const fullscreenApiIsPrefixed = "mozFullScreenEnabled" in document
+
+// Until firefox removes vendor prefix for this api (in FF64), we must also use mozfullscreenchange
+if (fullscreenApiIsPrefixed) {
+    document.addEventListener("mozfullscreenchange", fullscreenhandler)
+} else if ("fullscreenEnabled" in document) {
+    document.addEventListener("fullscreenchange", fullscreenhandler)
+}
 // }
 
 /** @hidden */
 //#content
-export async function loadaucmds(cmdType: "DocStart" | "DocLoad" | "DocEnd" | "TabEnter" | "TabLeft") {
+export async function loadaucmds(cmdType: "DocStart" | "DocLoad" | "DocEnd" | "TabEnter" | "TabLeft" | "FullscreenEnter" | "FullscreenLeft" | "FullscreenChange") {
     let aucmds = await config.getAsync("autocmds", cmdType)
     const ausites = Object.keys(aucmds)
     const aukeyarr = ausites.filter(e => window.document.location.href.search(e) >= 0)
@@ -3268,10 +3286,10 @@ export function set(key: string, ...values: string[]) {
 
 /** @hidden */
 //#background_helper
-let AUCMDS = ["DocStart", "DocLoad", "DocEnd", "TriStart", "TabEnter", "TabLeft"]
+let AUCMDS = ["DocStart", "DocLoad", "DocEnd", "TriStart", "TabEnter", "TabLeft", "FullscreenChange", "FullscreenEnter", "FullscreenLeft"]
 /** Set autocmds to run when certain events happen.
 
- @param event Curently, 'TriStart', 'DocStart', 'DocLoad', 'DocEnd', 'TabEnter' and 'TabLeft' are supported.
+ @param event Curently, 'TriStart', 'DocStart', 'DocLoad', 'DocEnd', 'TabEnter', 'TabLeft', 'FullscreenChange', 'FullscreenEnter', and 'FullscreenLeft' are supported
 
  @param url For DocStart, DocEnd, TabEnter, and TabLeft: a fragment of the URL on which the events will trigger, or a JavaScript regex (e.g, `/www\.amazon\.co.*\/`)
 
@@ -3313,7 +3331,7 @@ export function autocontain(domain: string, container: string) {
 }
 
 /** Remove autocmds
- @param event Curently, 'TriStart', 'DocStart', 'DocLoad', 'DocEnd', 'TabEnter' and 'TabLeft' are supported.
+ @param event Curently, 'TriStart', 'DocStart', 'DocLoad', 'DocEnd', 'TabEnter', 'TabLeft', 'FullscreenChange', 'FullscreenEnter', and 'FullscreenLeft' are supported
 
  @param url For DocStart, DocEnd, TabEnter, and TabLeft: a fragment of the URL on which the events will trigger, or a JavaScript regex (e.g, `/www\.amazon\.co.*\/`)
 */
diff --git a/src/lib/config.ts b/src/lib/config.ts
index ddc926d4..dc85f6dd 100644
--- a/src/lib/config.ts
+++ b/src/lib/config.ts
@@ -318,6 +318,21 @@ class default_config {
             // Too bad :/
             // "emacs.org": "tabclose",
         },
+
+        /**
+         * Commands that will be run when fullscreen state changes.
+         */
+        FullscreenChange: {},
+
+        /**
+         * Commands that will be run when fullscreen state is entered.
+         */
+        FullscreenEnter: {},
+
+        /**
+         * Commands that will be run when fullscreen state is left.
+         */
+        FullscreenLeft: {},
     }
 
     /**