diff --git a/index.d.ts b/index.d.ts
new file mode 100644
index 0000000..2804bce
--- /dev/null
+++ b/index.d.ts
@@ -0,0 +1,73 @@
+import { Server as HttpServer } from 'http';
+import { Server as HttpsServer, ServerOptions as NodeHttpsServerOptions } from 'https';
+import { Http2SecureServer, SecureServerOptions as NodeHttp2ServerOptions } from 'http2';
+
+type IPAddress = string;
+type FilePath = string;
+
+type PEMPath = string;
+type PEMData = string | Buffer;
+type PEM = PEMPath | PEMData;
+type PEMChain = PEM[];
+type PEMs = PEM | PEMChain;
+type CertificatePEMs = PEMs | PEMs[];
+
+type CommonOptions = {
+  timeout?: number,
+  handler?: Function,
+}
+
+type ServerOptions = CommonOptions & {
+  port?: number,
+  host: IPAddress,
+}
+
+type HttpOptions = ServerOptions;
+
+type TLSOptions = {
+  ciphers?: string,
+  honorCipherOrder?: boolean,
+  /**
+   * Required if ca, cert or key are FilePath
+   */
+  root?: FilePath,
+  key?: PEM,
+  cert?: CertificatePEMs,
+  ca?: PEMs,
+}
+
+type SNIOptions = {
+  sni?: {
+    [hostname: string]: TLSOptions
+  }
+}
+
+type HttpsOptions = ServerOptions & TLSOptions & SNIOptions & NodeHttpsServerOptions;
+
+type Http2Options = HttpsOptions & NodeHttp2ServerOptions;
+
+type Options = {
+  http?: HttpOptions | Array<HttpOptions>,
+  https?: HttpsOptions | Array<HttpsOptions>,
+  http2?: Http2Options | Array<Http2Options>,
+  handler?: Function,
+}
+
+type Errors = {
+  message: string,
+  http?: Error | Error[],
+  https?: Error | Error[],
+  http2?: Error | Error[],
+}
+
+type Servers = {
+  http?: HttpServer | HttpServer[],
+  https?: HttpsServer | HttpsServer[],
+  http2?: Http2SecureServer | Http2SecureServer[],
+}
+
+type Callback = (error?: Errors, servers?: Servers) => void;
+
+declare function createServers(options: Options, callback: Callback): void;
+
+export = createServers;
diff --git a/package-lock.json b/package-lock.json
index 30331e2..4b39703 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "create-servers",
-  "version": "3.2.0",
+  "version": "3.2.1",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
@@ -39,6 +39,12 @@
       "integrity": "sha512-+iTbntw2IZPb/anVDbypzfQa+ay64MW0Zo8aJ8gZPWMMK6/OubMVb6lUPMagqjOPnmtauXnFCACVl3O7ogjeqQ==",
       "dev": true
     },
+    "@types/node": {
+      "version": "16.3.3",
+      "resolved": "https://artifactory.secureserver.net/artifactory/api/npm/node-virt/@types/node/-/node-16.3.3.tgz",
+      "integrity": "sha1-DDCt/ze7vHpQ65tY+uKlBNDYgDg=",
+      "dev": true
+    },
     "array-from": {
       "version": "2.1.1",
       "resolved": "https://registry.npmjs.org/array-from/-/array-from-2.1.1.tgz",
diff --git a/package.json b/package.json
index 3c1cb8b..add4f24 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "create-servers",
-  "version": "3.2.0",
+  "version": "3.2.1",
   "description": "Create an http AND/OR an https server and call the same request handler.",
   "main": "index.js",
   "scripts": {
@@ -27,6 +27,7 @@
     "object-assign": "^4.1.0"
   },
   "devDependencies": {
+    "@types/node": "^16.3.3",
     "evil-dns": "^0.2.0",
     "sinon": "^5.0.7",
     "tape": "~4.9.0"