diff --git a/index.js b/index.js
index 7a0e9c2a123bc9d26c20bb3de4a3c4e49b24ee40..e750c4f51b436fae4cd82d58b43666442b95a3a3 100644
--- a/index.js
+++ b/index.js
@@ -377,6 +377,7 @@ Buffer.isEncoding = function isEncoding (encoding) {
     case 'latin1':
     case 'binary':
     case 'base64':
+    case 'base64url':
     case 'ucs2':
     case 'ucs-2':
     case 'utf16le':
@@ -466,6 +467,7 @@ function byteLength (string, encoding) {
       case 'hex':
         return len >>> 1
       case 'base64':
+      case 'base64url':
         return base64ToBytes(string).length
       default:
         if (loweredCase) {
@@ -534,6 +536,9 @@ function slowToString (encoding, start, end) {
       case 'base64':
         return base64Slice(this, start, end)
 
+      case 'base64url':
+        return base64urlSlice(this, start, end)
+
       case 'ucs2':
       case 'ucs-2':
       case 'utf16le':
@@ -917,6 +922,7 @@ Buffer.prototype.write = function write (string, offset, length, encoding) {
         return asciiWrite(this, string, offset, length)
 
       case 'base64':
+      case 'base64url':
         // Warning: maxLength not taken into account in base64Write
         return base64Write(this, string, offset, length)
 
@@ -949,6 +955,14 @@ function base64Slice (buf, start, end) {
   }
 }
 
+function base64urlSlice (buf, start, end) {
+  // base64url is base64 with a URL-safe alphabet and no padding
+  return base64Slice(buf, start, end)
+    .replace(/\+/g, '-')
+    .replace(/\//g, '_')
+    .replace(/=+$/, '')
+}
+
 function utf8Slice (buf, start, end) {
   end = Math.min(buf.length, end)
   const res = []
@@ -1942,6 +1956,9 @@ function base64clean (str) {
   str = str.split('=')[0]
   // Node strips out invalid characters like \n and \t from the string, base64-js does not
   str = str.trim().replace(INVALID_BASE64_RE, '')
+  // Translate the URL-safe base64url alphabet to standard base64 so that
+  // 'base64url'-encoded input decodes correctly via base64-js
+  str = str.replace(/-/g, '+').replace(/_/g, '/')
   // Node converts strings with length < 2 to ''
   if (str.length < 2) return ''
   // Node allows for non-padded base64 strings (missing trailing ===), base64-js does not