diff --git a/package.json b/package.json
index 3669ab9..e352e42 100644
--- a/package.json
+++ b/package.json
@@ -38,6 +38,13 @@
     "stream-to-it": "^0.2.0"
   },
   "devDependencies": {
+    "@types/chai": "^4.2.11",
+    "@types/chai-as-promised": "^7.1.2",
+    "@types/dirty-chai": "^2.0.2",
+    "@types/fs-extra": "^8.1.0",
+    "@types/it-all": "^1.0.0",
+    "@types/node": "^13.9.3",
+    "@types/node-fetch": "^2.5.5",
     "aegir": "^21.4.2",
     "chai": "^4.2.0",
     "chai-as-promised": "^7.1.1",
diff --git a/src/env.d.ts b/src/env.d.ts
new file mode 100644
index 0000000..b03177b
--- /dev/null
+++ b/src/env.d.ts
@@ -0,0 +1,12 @@
+declare const IS_TEST: boolean;
+declare const IS_ELECTRON: any;
+declare const IS_ELECTRON_MAIN: boolean;
+declare const IS_ELECTRON_RENDERER: boolean;
+declare const IS_NODE: boolean;
+/**
+ * Detects browser main thread  **NOT** web worker or service worker
+ */
+declare const IS_BROWSER: boolean;
+declare const IS_WEBWORKER: boolean;
+declare const IS_ENV_WITH_DOM: boolean;
+export { IS_TEST as isTest, IS_ELECTRON as isElectron, IS_ELECTRON_MAIN as isElectronMain, IS_ELECTRON_RENDERER as isElectronRenderer, IS_NODE as isNode, IS_BROWSER as isBrowser, IS_WEBWORKER as isWebWorker, IS_ENV_WITH_DOM as isEnvWithDom };
diff --git a/src/files/format-mode.d.ts b/src/files/format-mode.d.ts
new file mode 100644
index 0000000..008c0c6
--- /dev/null
+++ b/src/files/format-mode.d.ts
@@ -0,0 +1,2 @@
+export = formatMode;
+declare function formatMode(mode: number, isDirectory: boolean): string;
diff --git a/src/files/format-mode.js b/src/files/format-mode.js
index f25ae5c..cab76af 100644
--- a/src/files/format-mode.js
+++ b/src/files/format-mode.js
@@ -16,6 +16,13 @@ const S_IROTH = parseInt('4', 8) //      others have read permission
 const S_IWOTH = parseInt('2', 8) //      others have write permission
 const S_IXOTH = parseInt('1', 8) //      others have execute permission
 
+/**
+ *
+ * @param {number} mode
+ * @param {number} perm
+ * @param {string} type
+ * @param {string[]} output
+ */
 function checkPermission (mode, perm, type, output) {
   if ((mode & perm) === perm) {
     output.push(type)
@@ -24,6 +31,12 @@ function checkPermission (mode, perm, type, output) {
   }
 }
 
+/**
+ *
+ * @param {number} mode
+ * @param {boolean} isDirectory
+ * @returns {string}
+ */
 function formatMode (mode, isDirectory) {
   const output = []
 
diff --git a/src/files/format-mtime.d.ts b/src/files/format-mtime.d.ts
new file mode 100644
index 0000000..e5c6175
--- /dev/null
+++ b/src/files/format-mtime.d.ts
@@ -0,0 +1,2 @@
+export = formatMtime;
+declare function formatMtime(mtime: { secs: number, nsecs: number }): string;
diff --git a/src/files/glob-source.d.ts b/src/files/glob-source.d.ts
new file mode 100644
index 0000000..f7c1321
--- /dev/null
+++ b/src/files/glob-source.d.ts
@@ -0,0 +1,24 @@
+/// <reference types="node" />
+import { ReadStream } from "fs";
+/**
+* Create an async iterator that yields paths that match requested file paths.
+*
+* @param {Iterable|AsyncIterable|String} paths File system path(s) to glob from
+* @param {Object} [options] Optional options
+* @param {Boolean} [options.recursive] Recursively glob all paths in directories
+* @param {Boolean} [options.hidden] Include .dot files in matched paths
+* @param {Array<String>} [options.ignore] Glob paths to ignore
+* @param {Boolean} [options.followSymlinks] follow symlinks
+* @param {Boolean} [options.preserveMode] preserve mode
+* @param {Boolean} [options.preserveMtime] preserve mtime
+* @param {Boolean} [options.mode] mode to use - if preserveMode is true this will be ignored
+* @param {Boolean} [options.mtime] mtime to use - if preserveMtime is true this will be ignored
+* @yields {{ path: String, content: AsyncIterator<Buffer> }} File objects in the form `{ path: String, content: AsyncIterator<Buffer> }`
+*/
+declare function globSource(paths: Iterable<string> | AsyncIterable<string> | string, options: any): AsyncGenerator<{
+    path: string;
+    content?: ReadStream;
+    mode: number;
+    mtime: number;
+}>;
+export = globSource;
diff --git a/src/files/normalise-input.d.ts b/src/files/normalise-input.d.ts
new file mode 100644
index 0000000..99b2fe1
--- /dev/null
+++ b/src/files/normalise-input.d.ts
@@ -0,0 +1,6 @@
+declare function _exports(input: any): AsyncGenerator<{
+    path: string;
+    mode: number;
+    mtime: number;
+}>;
+export = _exports;
diff --git a/src/files/url-source.d.ts b/src/files/url-source.d.ts
new file mode 100644
index 0000000..eb5babd
--- /dev/null
+++ b/src/files/url-source.d.ts
@@ -0,0 +1,5 @@
+declare function _exports(url: any, options: any): AsyncGenerator<{
+    path: string;
+    content: AsyncGenerator<Uint8Array>;
+}>;
+export = _exports;
diff --git a/src/globalthis.d.ts b/src/globalthis.d.ts
new file mode 100644
index 0000000..73d760f
--- /dev/null
+++ b/src/globalthis.d.ts
@@ -0,0 +1,2 @@
+declare const _exports: typeof globalThis;
+export = _exports;
diff --git a/src/http.d.ts b/src/http.d.ts
new file mode 100644
index 0000000..209ab32
--- /dev/null
+++ b/src/http.d.ts
@@ -0,0 +1,141 @@
+export = HTTP;
+/**
+ * @typedef {Object} APIOptions - creates a new type named 'SpecialType'
+ * @prop {any} [body] - Request body
+ * @prop {string} [method] - GET, POST, PUT, DELETE, etc.
+ * @prop {string} [base] - The base URL to use in case url is a relative URL
+ * @prop {Headers|Record<string, string>} [headers] - Request header.
+ * @prop {number} [timeout] - Amount of time until request should timeout in ms.
+ * @prop {AbortSignal} [signal] - Signal to abort the request.
+ * @prop {URLSearchParams|Object} [searchParams] - URL search param.
+ * @prop {string} [credentials]
+ * @prop {boolean} [throwHttpErrors]
+ * @prop {function(URLSearchParams): URLSearchParams } [transformSearchParams]
+ * @prop {function(any): any} [transform] - When iterating the response body, transform each chunk with this function.
+ * @prop {function(Response): Promise<void>} [handleError] - Handle errors
+ */
+declare class HTTP {
+    /**
+     *
+     * @param {APIOptions} options
+     */
+    constructor(options?: APIOptions);
+    /** @type {APIOptions} */
+    opts: APIOptions;
+    abortController: any;
+    /**
+     * Fetch
+     *
+     * @param {string | URL | Request} resource
+     * @param {APIOptions} options
+     * @returns {Promise<Response>}
+     */
+    fetch(resource: string | Request | URL, options?: APIOptions): Promise<Response>;
+    /**
+     * @param {string | URL | Request} resource
+     * @param {APIOptions} options
+     * @returns {Promise<Response>}
+     */
+    post(resource: string | Request | URL, options?: APIOptions): Promise<Response>;
+    /**
+     * @param {string | URL | Request} resource
+     * @param {APIOptions} options
+     * @returns {Promise<Response>}
+     */
+    get(resource: string | Request | URL, options?: APIOptions): Promise<Response>;
+    /**
+     * @param {string | URL | Request} resource
+     * @param {APIOptions} options
+     * @returns {Promise<Response>}
+     */
+    put(resource: string | Request | URL, options?: APIOptions): Promise<Response>;
+    /**
+     * @param {string | URL | Request} resource
+     * @param {APIOptions} options
+     * @returns {Promise<Response>}
+     */
+    delete(resource: string | Request | URL, options?: APIOptions): Promise<Response>;
+    /**
+     * @param {string | URL | Request} resource
+     * @param {APIOptions} options
+     * @returns {Promise<Response>}
+     */
+    options(resource: string | Request | URL, options?: APIOptions): Promise<Response>;
+    /**
+     * @param {string | URL | Request} resource
+     * @param {APIOptions} options
+     * @returns {Promise<ReadableStream<Uint8Array>>}
+     */
+    stream(resource: string | Request | URL, options?: APIOptions): Promise<ReadableStream<Uint8Array>>;
+    /**
+     * @param {string | URL | Request} resource
+     * @param {APIOptions} options
+     * @returns {AsyncGenerator<Uint8Array, void, any>}
+     */
+    iterator(resource: string | Request | URL, options?: APIOptions): AsyncGenerator<Uint8Array, void, any>;
+    /**
+     * @param {string | URL | Request} resource
+     * @param {APIOptions} options
+     * @returns {AsyncGenerator<Object, void, any>}
+     */
+    ndjson(resource: string | Request | URL, options?: APIOptions): AsyncGenerator<any, void, any>;
+}
+declare namespace HTTP {
+    export { HTTPError, TimeoutError, ndjson, streamToAsyncIterator, post, get, put, _delete as delete, options, APIOptions };
+}
+/**
+ * - creates a new type named 'SpecialType'
+ */
+type APIOptions = {
+    /**
+     * - Request body
+     */
+    body?: any;
+    /**
+     * - GET, POST, PUT, DELETE, etc.
+     */
+    method?: string;
+    /**
+     * - The base URL to use in case url is a relative URL
+     */
+    base?: string;
+    /**
+     * - Request header.
+     */
+    headers?: Record<string, string> | Headers;
+    /**
+     * - Amount of time until request should timeout in ms.
+     */
+    timeout?: number;
+    /**
+     * - Signal to abort the request.
+     */
+    signal?: AbortSignal;
+    /**
+     * - URL search param.
+     */
+    searchParams?: any;
+    credentials?: string;
+    throwHttpErrors?: boolean;
+    transformSearchParams?: (arg0: URLSearchParams) => URLSearchParams;
+    /**
+     * - When iterating the response body, transform each chunk with this function.
+     */
+    transform?: (arg0: any) => any;
+    /**
+     * - Handle errors
+     */
+    handleError?: (arg0: Response) => Promise<void>;
+};
+declare class HTTPError extends Error {
+    constructor(response: any);
+    response: any;
+}
+declare class TimeoutError extends Error {
+}
+declare function ndjson(source: AsyncGenerator<Uint8Array, void, any>): AsyncGenerator<any, void, any>;
+declare function streamToAsyncIterator(source: any): any;
+declare function post(resource: string | Request | URL, options: APIOptions): Promise<Response>;
+declare function get(resource: string | Request | URL, options: APIOptions): Promise<Response>;
+declare function put(resource: string | Request | URL, options: APIOptions): Promise<Response>;
+declare function options(resource: string | Request | URL, options: APIOptions): Promise<Response>;
diff --git a/src/supports.d.ts b/src/supports.d.ts
new file mode 100644
index 0000000..cd494ca
--- /dev/null
+++ b/src/supports.d.ts
@@ -0,0 +1 @@
+export declare const supportsFileReader: boolean;
diff --git a/src/text-encoder.browser.d.ts b/src/text-encoder.browser.d.ts
new file mode 100644
index 0000000..f1e0f6a
--- /dev/null
+++ b/src/text-encoder.browser.d.ts
@@ -0,0 +1,4 @@
+import { TextDecoder } from 'util'
+
+declare const _exports: typeof TextDecoder;
+export = _exports;
diff --git a/src/text-encoder.d.ts b/src/text-encoder.d.ts
new file mode 100644
index 0000000..f1e0f6a
--- /dev/null
+++ b/src/text-encoder.d.ts
@@ -0,0 +1,4 @@
+import { TextDecoder } from 'util'
+
+declare const _exports: typeof TextDecoder;
+export = _exports;
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..fdb4c6e
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,8 @@
+{
+  "compilerOptions": {
+    "target": "ESNext",
+    "declaration": true,
+    "emitDeclarationOnly": true,
+    "allowJs": true
+  }
+}