diff --git a/README.md b/README.md
index 4d6ae71..7274ce9 100644
--- a/README.md
+++ b/README.md
@@ -4,7 +4,7 @@
 [![NPM Downloads](https://img.shields.io/npm/dm/base64-arraybuffer.svg)](https://www.npmjs.org/package/base64-arraybuffer)
 [![NPM Version](https://img.shields.io/npm/v/base64-arraybuffer.svg)](https://www.npmjs.org/package/base64-arraybuffer)
 
-Encode/decode base64 data into ArrayBuffers
+Encode/decode base64 or base64url data into ArrayBuffers.
 
 ### Installing
 You can install the module via npm:
@@ -12,11 +12,14 @@ You can install the module via npm:
     npm install base64-arraybuffer
   
 ## API
-The library encodes and decodes base64 to and from ArrayBuffers
+The library encodes and decodes base64/base64url to and from ArrayBuffers
 
  - __encode(buffer)__ - Encodes `ArrayBuffer` into base64 string
  - __decode(str)__ - Decodes base64 string to `ArrayBuffer`
 
+ - __encode(buffer, true)__ - Encodes `ArrayBuffer` into base64url string
+ - __decode(str, true)__ - Decodes base64url string to `ArrayBuffer`
+
 ### Testing
 You can run the test suite with:
 
diff --git a/package-lock.json b/package-lock.json
index 1960bad..4fa9beb 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -5,6 +5,7 @@
   "requires": true,
   "packages": {
     "": {
+      "name": "base64-arraybuffer",
       "version": "1.0.1",
       "license": "MIT",
       "devDependencies": {
diff --git a/src/index.ts b/src/index.ts
index 2de9733..0227e11 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,34 +1,43 @@
-const chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
+const 
+    chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/',
+    charsUrl = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_',
 
-// Use a lookup table to find the index.
-const lookup = typeof Uint8Array === 'undefined' ? [] : new Uint8Array(256);
-for (let i = 0; i < chars.length; i++) {
-    lookup[chars.charCodeAt(i)] = i;
-}
+    genLookup = (target: string) => {
+        let lookupTemp = typeof Uint8Array === 'undefined' ? [] : new Uint8Array(256);
+        for (let i = 0; i < chars.length; i++) {
+            lookupTemp[target.charCodeAt(i)] = i;
+        }
+        return lookupTemp;
+    },
+    
+    // Use a lookup table to find the index.
+    lookup = genLookup(chars),
+    lookupUrl = genLookup(charsUrl); 
 
-export const encode = (arraybuffer: ArrayBuffer): string => {
+export const encode = (arraybuffer: ArrayBuffer, urlMode?: boolean): string => {
     let bytes = new Uint8Array(arraybuffer),
         i,
         len = bytes.length,
-        base64 = '';
+        base64 = '',
+        target = urlMode ? charsUrl : chars;
 
     for (i = 0; i < len; i += 3) {
-        base64 += chars[bytes[i] >> 2];
-        base64 += chars[((bytes[i] & 3) << 4) | (bytes[i + 1] >> 4)];
-        base64 += chars[((bytes[i + 1] & 15) << 2) | (bytes[i + 2] >> 6)];
-        base64 += chars[bytes[i + 2] & 63];
+        base64 += target[bytes[i] >> 2];
+        base64 += target[((bytes[i] & 3) << 4) | (bytes[i + 1] >> 4)];
+        base64 += target[((bytes[i + 1] & 15) << 2) | (bytes[i + 2] >> 6)];
+        base64 += target[bytes[i + 2] & 63];
     }
 
     if (len % 3 === 2) {
-        base64 = base64.substring(0, base64.length - 1) + '=';
+        base64 = base64.substring(0, base64.length - 1) + (urlMode ? '' : '=');
     } else if (len % 3 === 1) {
-        base64 = base64.substring(0, base64.length - 2) + '==';
+        base64 = base64.substring(0, base64.length - 2) + (urlMode ? '' : '==');
     }
 
     return base64;
 };
 
-export const decode = (base64: string): ArrayBuffer => {
+export const decode = (base64: string, urlMode?: boolean): ArrayBuffer => {
     let bufferLength = base64.length * 0.75,
         len = base64.length,
         i,
@@ -45,14 +54,16 @@ export const decode = (base64: string): ArrayBuffer => {
         }
     }
 
-    const arraybuffer = new ArrayBuffer(bufferLength),
-        bytes = new Uint8Array(arraybuffer);
+    const 
+        arraybuffer = new ArrayBuffer(bufferLength),
+        bytes = new Uint8Array(arraybuffer),
+        target = urlMode ? lookupUrl : lookup;
 
     for (i = 0; i < len; i += 4) {
-        encoded1 = lookup[base64.charCodeAt(i)];
-        encoded2 = lookup[base64.charCodeAt(i + 1)];
-        encoded3 = lookup[base64.charCodeAt(i + 2)];
-        encoded4 = lookup[base64.charCodeAt(i + 3)];
+        encoded1 = target[base64.charCodeAt(i)];
+        encoded2 = target[base64.charCodeAt(i + 1)];
+        encoded3 = target[base64.charCodeAt(i + 2)];
+        encoded4 = target[base64.charCodeAt(i + 3)];
 
         bytes[p++] = (encoded1 << 2) | (encoded2 >> 4);
         bytes[p++] = ((encoded2 & 15) << 4) | (encoded3 >> 2);
diff --git a/test/base64-arraybuffer.ts b/test/base64-arraybuffer.ts
index 6d6f4be..0667f22 100644
--- a/test/base64-arraybuffer.ts
+++ b/test/base64-arraybuffer.ts
@@ -68,3 +68,34 @@ describe('decode', () => {
             )
         ));
 });
+
+
+describe('encode url', () => {
+    it('encode "Hello world"', () => equal(encode(stringArrayBuffer('Hello world'), true), 'SGVsbG8gd29ybGQ'));
+    it('encode "Man"', () => equal(encode(stringArrayBuffer('Man'), true), 'TWFu'));
+    it('encode "Ma"', () => equal(encode(stringArrayBuffer('Ma'), true), 'TWE'));
+    it('encode "Hello worlds!"', () => equal(encode(stringArrayBuffer('Hello worlds!'), true), 'SGVsbG8gd29ybGRzIQ'));
+    it('encode all binary characters', () =>
+        equal(
+            encode(rangeArrayBuffer(), true),
+            'AAECAwQFBgcICQoLDA0ODxAREhMUFRYXGBkaGxwdHh8gISIjJCUmJygpKissLS4vMDEyMzQ1Njc4OTo7PD0-P0BBQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWltcXV5fYGFiY2RlZmdoaWprbG1ub3BxcnN0dXZ3eHl6e3x9fn-AgYKDhIWGh4iJiouMjY6PkJGSk5SVlpeYmZqbnJ2en6ChoqOkpaanqKmqq6ytrq-wsbKztLW2t7i5uru8vb6_wMHCw8TFxsfIycrLzM3Oz9DR0tPU1dbX2Nna29zd3t_g4eLj5OXm5-jp6uvs7e7v8PHy8_T19vf4-fr7_P3-_w'
+        ));
+});
+
+describe('decode url', () => {
+    it('decode "Man"', () => ok(testArrayBuffers(decode('TWFu', true), stringArrayBuffer('Man'))));
+    it('decode "Hello world"', () =>
+        ok(testArrayBuffers(decode('SGVsbG8gd29ybGQ', true), stringArrayBuffer('Hello world'))));
+    it('decode "Hello worlds!"', () =>
+        ok(testArrayBuffers(decode('SGVsbG8gd29ybGRzIQ', true), stringArrayBuffer('Hello worlds!'))));
+    it('decode all binary characters', () =>
+        ok(
+            testArrayBuffers(
+                decode(
+                    'AAECAwQFBgcICQoLDA0ODxAREhMUFRYXGBkaGxwdHh8gISIjJCUmJygpKissLS4vMDEyMzQ1Njc4OTo7PD0-P0BBQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWltcXV5fYGFiY2RlZmdoaWprbG1ub3BxcnN0dXZ3eHl6e3x9fn-AgYKDhIWGh4iJiouMjY6PkJGSk5SVlpeYmZqbnJ2en6ChoqOkpaanqKmqq6ytrq-wsbKztLW2t7i5uru8vb6_wMHCw8TFxsfIycrLzM3Oz9DR0tPU1dbX2Nna29zd3t_g4eLj5OXm5-jp6uvs7e7v8PHy8_T19vf4-fr7_P3-_w',
+                    true
+                ),
+                rangeArrayBuffer()
+            )
+        ));
+});
\ No newline at end of file