diff --git a/types/twitch-ext/index.d.ts b/types/twitch-ext/index.d.ts
new file mode 100644
index 0000000000..279d17cd14
--- /dev/null
+++ b/types/twitch-ext/index.d.ts
@@ -0,0 +1,330 @@
+// Type definitions for twitch-ext 1.14
+// Project: https://dev.twitch.tv/docs/extensions/reference/#javascript-helper
+// Definitions by: Benedict Etzel <https://github.com/beheh>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+// TypeScript Version: 2.4
+
+interface Window {
+	Twitch: { ext: TwitchExt };
+}
+
+/**
+ * The Twitch extensions JavaScript Helper.
+ *
+ * @see https://dev.twitch.tv/docs/extensions/reference/#javascript-helper
+ */
+interface TwitchExt {
+	/**
+	 * This encodes the Helper version in 1.1.1 (semantic versioning) format.
+	 */
+	version: string;
+
+	/**
+	 * This encodes the environment. For external users, this is always production.
+	 */
+	environment: "production";
+
+	/**
+	 * @see https://dev.twitch.tv/docs/extensions/reference/#twitch-extension-actions
+	 */
+	actions: TwitchExtActions;
+
+	/**
+	 * Helper methods for the Twitch Extension rig.
+	 * @see https://github.com/twitchdev/developer-rig
+	 */
+	rig: TwitchExtRig;
+
+	/**
+	 * This function binds the callback to the initial values and changes to the authorization data.
+	 *
+	 * @param authCallback This callback is fired each time the JWT is refreshed.
+	 * @see https://dev.twitch.tv/docs/extensions/reference/#onauthorized
+	 */
+	onAuthorized(authCallback: (auth: TwitchExtAuthorized) => void): void;
+
+	/**
+	 * This function binds the callback to the initial values and changes to the context.
+	 *
+	 * @param contextCallback This callback is fired when the context of an extension is fired.
+	 * @see https://dev.twitch.tv/docs/extensions/reference/#oncontext
+	 */
+	onContext(
+		contextCallback: <T extends Partial<TwitchExtContext>>(
+			context: T,
+			changed: ReadonlyArray<keyof T>
+		) => void
+	): void;
+
+	/**
+	 * This function binds the callback to any internal error.
+	 *
+	 * @param errorCallback This callback is fired if any errors are generated by the extension helper.
+	 * @see https://dev.twitch.tv/docs/extensions/reference/#onerror
+	 */
+	onError(errorCallback: (errorValue: any) => void): void;
+
+	/**
+	 * This function registers a callback that gets called whenever an extension changes position in the player. This
+	 * occurs only for video-component extensions. This also is triggered as the extension loads.
+	 *
+	 * @param callback This callback is called whenever an extension changes position in the player.
+	 * @see https://dev.twitch.tv/docs/extensions/reference/#onpositionchanged
+	 */
+	onPositionChanged(
+		callback: (position: { x: number; y: number }) => void
+	): void;
+
+	/**
+	 * This function registers a callback that gets called whenever an extension is hidden/re-shown. (This occurs only
+	 * for mobile or component extensions.) When an extension is not visible in the mobile app, it does not receive
+	 * onContext updates and must perform only minimal work in the background.
+	 *
+	 * @param callback This callback is called whenever an extension is hidden/re-shown.
+	 * @see https://dev.twitch.tv/docs/extensions/reference/#onvisibilitychanged
+	 */
+	onVisibilityChanged(
+		callback:
+			| ((isVisible: false) => void)
+			| ((isVisible: true, context: Partial<TwitchExtContext>) => void)
+	): void;
+
+	/**
+	 * This function can be called by the front end to send directly to PubSub.
+	 *
+	 * @param target Target topic. Often this is "broadcast" but it might be "whisper-<userId>".
+	 * @param contentType type of the serialized message; for example, "application/json".
+	 * @param message Either an object that will be automatically serialized as JSON or a string.
+	 * @see https://dev.twitch.tv/docs/extensions/reference/#send
+	 */
+	send(target: string, contentType: string, message: object | string): void;
+
+	/**
+	 * This function binds the callback to listen to the target topic.
+	 *
+	 * @param target Target topic. Often this is "broadcast" but it might be "whisper-<userId>".
+	 * @param callback These fields correspond to the values in the send() message, except the message is always a string.
+	 * @see https://dev.twitch.tv/docs/extensions/reference/#listen
+	 */
+	listen(
+		target: string,
+		callback: (target: string, contentType: string, message: string) => void
+	): void;
+
+	/**
+	 * This function unbinds the listen callback from the target.
+	 *
+	 * @param target Target topic. Often this is "broadcast" but it might be "whisper-<userId>".
+	 * @param callback These fields correspond to the values in the send() message, except the message is always a string.
+	 * @see https://dev.twitch.tv/docs/extensions/reference/#unlisten
+	 */
+	unlisten(
+		target: string,
+		callback: (target: string, contentType: string, message: string) => void
+	): void;
+}
+
+/**
+ * Twitch actions add first-party Twitch functionality to extensions.
+ *
+ * @see TwitchExt.actions
+ */
+interface TwitchExtActions {
+	/**
+	 * This function prompts users to follow the specified channel, with a dialog controlled by Twitch.
+	 *
+	 * @see https://dev.twitch.tv/docs/extensions/reference/#followchannel
+	 */
+	followChannel(channelName: string): void;
+
+	/**
+	 * This function registers a callback that is invoked whenever a user completes an interaction prompted by the followChannel action.
+	 *
+	 * @see https://dev.twitch.tv/docs/extensions/reference/#onfollow
+	 */
+	onFollow(callback: (didFollow: boolean, channelName: string) => void): void;
+
+	/**
+	 * This function opens a prompt for users to share their identity.
+	 * After a successful identity link, the Twitch.ext.onAuthorized callback is invoked with the user’s ID.
+	 *
+	 * @see https://dev.twitch.tv/docs/extensions/reference/#requestidshare
+	 */
+	requestIdShare(): void;
+}
+
+/**
+ * The developer rig object as available under window.Twitch.ext.rig.
+ *
+ * @see TwitchExt.rig
+ */
+interface TwitchExtRig {
+	/**
+	 * Print a message to the developer rig console.
+	 *
+	 * @param message The message to print.
+	 * @see https://github.com/twitchdev/developer-rig#rig-console
+	 */
+	log(message: string): void;
+}
+
+/**
+ * The result object as passed to the onAuthorized callback.
+ *
+ * @see TwitchExt.onAuthorized
+ */
+interface TwitchExtAuthorized {
+	/**
+	 * Channel ID of the page where the extension is iframe embedded.
+	 */
+	channelId: string;
+
+	/**
+	 * Client ID of the extension.
+	 */
+	clientId: string;
+
+	/**
+	 * JWT that should be passed to any EBS call for authentication.
+	 */
+	token: string;
+
+	/**
+	 * Opaque user ID.
+	 */
+	userId: string;
+}
+
+/**
+ * The result object as passed to the onContext callback.
+ *
+ * @see TwitchExt.onContext
+ */
+interface TwitchExtContext {
+	/**
+	 * If true, player controls are visible (e.g., due to mouseover).
+	 * Do not use this for mobile extensions; it is not sent for mobile.
+	 */
+	arePlayerControlsVisible: boolean;
+
+	/**
+	 * Bitrate of the broadcast.
+	 */
+	bitrate: number;
+
+	/**
+	 * Buffer size of the broadcast.
+	 */
+	bufferSize: number;
+
+	/**
+	 * Display size of the player.
+	 */
+	displayResolution: string;
+
+	/**
+	 * Game being broadcast.
+	 */
+	game: string;
+
+	/**
+	 * Number of seconds of latency between the broadcaster and viewer.
+	 */
+	hlsLatencyBroadcaster: number;
+
+	/**
+	 * If true, the viewer is watching in fullscreen mode.
+	 * Do not use this for mobile extensions; it is not sent for mobile.
+	 */
+	isFullScreen: boolean;
+
+	/**
+	 * If true, the viewer has muted the stream.
+	 */
+	isMuted: boolean;
+
+	/**
+	 * If true, the viewer has paused the stream.
+	 */
+	isPaused: boolean;
+
+	/**
+	 * If true, the viewer is watching in theater mode.
+	 * Do not use this for mobile extensions; it is not sent for mobile.
+	 */
+	isTheatreMode: boolean;
+
+	/**
+	 * Language of the broadcast (e.g., "en").
+	 */
+	language: string;
+
+	/**
+	 * The mode the extension is currently run in.
+	 */
+	mode: "viewer" | "dashboard" | "config";
+
+	/**
+	 * Indicates how the stream is being played.
+	 */
+	playbackMode: "video" | "audio" | "remote" | "chat-only";
+
+	/**
+	 * The user’s theme setting on the Twitch website.
+	 */
+	theme: "light" | "dark";
+
+	/**
+	 * Resolution of the broadcast.
+	 */
+	videoResolution: string;
+
+	/**
+	 * Currently selected player volume. Valid values: between 0 and 1.
+	 */
+	volume: number;
+}
+
+/**
+ * The extension window receives the following query parameters, which indicate
+ * information about the extension environment that isn’t subject to change over
+ * the frame’s life cycle.
+ *
+ * @see https://dev.twitch.tv/docs/extensions/reference/#client-query-parameters
+ */
+interface TwitchExtClientQueryParams {
+	/**
+	 * The type of the anchor in which the extension is activated.
+	 */
+	anchor: "component" | "panel" | "video_overlay";
+
+	/**
+	 * The user’s language setting.
+	 *
+	 * @example en
+	 */
+	language: string;
+
+	/**
+	 * The extension’s mode.
+	 */
+	mode: "config" | "dashboard" | "viewer";
+
+	/**
+	 * The platform on which the Twitch client is running.
+	 */
+	platform: "mobile" | "web";
+
+	/**
+	 * The release state of the extension.
+	 */
+	state:
+		| "testing"
+		| "hosted_test"
+		| "approved"
+		| "released"
+		| "ready_for_review"
+		| "in_review"
+		| "pending_action"
+		| "uploading";
+}
diff --git a/types/twitch-ext/tsconfig.json b/types/twitch-ext/tsconfig.json
new file mode 100644
index 0000000000..5b68367453
--- /dev/null
+++ b/types/twitch-ext/tsconfig.json
@@ -0,0 +1,24 @@
+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "lib": [
+            "es6",
+            "dom"
+        ],
+        "noImplicitAny": true,
+        "noImplicitThis": true,
+        "strictNullChecks": true,
+        "strictFunctionTypes": true,
+        "baseUrl": "../",
+        "typeRoots": [
+            "../"
+        ],
+        "types": [],
+        "noEmit": true,
+        "forceConsistentCasingInFileNames": true
+    },
+    "files": [
+        "index.d.ts",
+        "twitch-ext-tests.ts"
+    ]
+}
diff --git a/types/twitch-ext/tslint.json b/types/twitch-ext/tslint.json
new file mode 100644
index 0000000000..3db14f85ea
--- /dev/null
+++ b/types/twitch-ext/tslint.json
@@ -0,0 +1 @@
+{ "extends": "dtslint/dt.json" }
diff --git a/types/twitch-ext/twitch-ext-tests.ts b/types/twitch-ext/twitch-ext-tests.ts
new file mode 100644
index 0000000000..d981367fd5
--- /dev/null
+++ b/types/twitch-ext/twitch-ext-tests.ts
@@ -0,0 +1,39 @@
+console.log(
+	`Running ${window.Twitch.ext.version} on ${window.Twitch.ext.environment}`
+);
+
+window.Twitch.ext.onAuthorized(auth => {
+	console.log("The JWT that will be passed to the EBS is", auth.token);
+	console.log("The channel ID is", auth.channelId);
+});
+
+window.Twitch.ext.onContext((context, changed) => {
+	for (const key of changed) {
+		console.log(`Context changed ${context[key]}`);
+	}
+});
+
+window.Twitch.ext.onVisibilityChanged((isVisible, context) => {
+	if (isVisible) {
+		console.log("Extension became visible");
+		if (context.game) {
+			console.log(`Current game is ${context.game}`);
+		}
+	} else {
+		console.log("Extension became invisible");
+	}
+});
+
+window.Twitch.ext.onError(e => console.error(e));
+
+// Twitch Extension Actions
+window.Twitch.ext.actions.onFollow((didFollow, channelName) => {
+	if (didFollow) {
+		console.log(`You followed ${channelName}`);
+	}
+});
+window.Twitch.ext.actions.followChannel("hearthsim");
+window.Twitch.ext.actions.requestIdShare();
+
+// Developer Rig
+window.Twitch.ext.rig.log("Hello, world!");