diff --git a/samples/advanced/extend.html b/samples/advanced/extend.html
index 27e9151a9f..e8e86e93e5 100644
--- a/samples/advanced/extend.html
+++ b/samples/advanced/extend.html
@@ -38,7 +38,24 @@
                     modifyRequestURL: function (url) {
                         /* Modify url adding a custom query string parameter */
                         return url + '?customQuery=value';
-                    }
+                    },
+                    modifyRequest(request) {
+                        /* Modify the entire request. Allows for async modifications */
+                        var url = new URL(request.url);
+
+                        if (!/\.mpd$/.test(url.pathname)) {
+                            return;
+                        }
+
+                        return fetch('https://time.akamai.com')
+                            .then(function (response) {
+                                return response.text();
+                            })
+                            .then(function (text) {
+                                url.searchParams.set('now', text);
+                                request.url = url.toString();
+                            });
+                    },
                 };
             });
             player.initialize(video, url, true);
diff --git a/src/streaming/net/FetchLoader.js b/src/streaming/net/FetchLoader.js
index b35339ed01..f8aa23fefa 100644
--- a/src/streaming/net/FetchLoader.js
+++ b/src/streaming/net/FetchLoader.js
@@ -32,6 +32,7 @@
 import FactoryMaker from '../../core/FactoryMaker';
 import Settings from '../../core/Settings';
 import Constants from '../constants/Constants';
+import { modifyRequest } from '../utils/RequestModifier';
 
 /**
  * @module FetchLoader
@@ -54,7 +55,16 @@ function FetchLoader(cfg) {
     }
 
     function load(httpRequest) {
+        if (requestModifier && requestModifier.modifyRequest) {
+            modifyRequest(httpRequest, requestModifier)
+                .then(() => request(httpRequest));
+        }
+        else {
+            request(httpRequest);
+        }
+    }
 
+    function request(httpRequest) {
         // Variables will be used in the callback functions
         const requestStartTime = new Date();
         const request = httpRequest.request;
@@ -77,7 +87,7 @@ function FetchLoader(cfg) {
             request.requestStartDate = requestStartTime;
         }
 
-        if (requestModifier) {
+        if (requestModifier && requestModifier.modifyRequestHeader) {
             // modifyRequestHeader expects a XMLHttpRequest object so,
             // to keep backward compatibility, we should expose a setRequestHeader method
             // TODO: Remove RequestModifier dependency on XMLHttpRequest object and define
@@ -176,7 +186,7 @@ function FetchLoader(cfg) {
                             reader.read().then(function processFetch(args) {
                                 const value = args.value;
                                 const done = args.done;
-                                markB = Date.now()
+                                markB = Date.now();
 
                                 if (value && value.length) {
                                     const chunkDownloadDurationMS = markB - markA;
diff --git a/src/streaming/net/HTTPLoader.js b/src/streaming/net/HTTPLoader.js
index 26ec382903..8e13addd27 100644
--- a/src/streaming/net/HTTPLoader.js
+++ b/src/streaming/net/HTTPLoader.js
@@ -271,7 +271,7 @@ function HTTPLoader(cfg) {
         }
 
         let headers = null;
-        let modifiedUrl = requestModifier.modifyRequestURL(request.url);
+        let modifiedUrl = requestModifier.modifyRequestURL ? requestModifier.modifyRequestURL(request.url) : request.url;
         if (settings.get().streaming.cmcd && settings.get().streaming.cmcd.enabled) {
             const cmcdMode = settings.get().streaming.cmcd.mode;
             if (cmcdMode === Constants.CMCD_MODE_QUERY) {
diff --git a/src/streaming/net/XHRLoader.js b/src/streaming/net/XHRLoader.js
index cd58bd7daf..f62d24056d 100644
--- a/src/streaming/net/XHRLoader.js
+++ b/src/streaming/net/XHRLoader.js
@@ -29,6 +29,7 @@
  *  POSSIBILITY OF SUCH DAMAGE.
  */
 import FactoryMaker from '../../core/FactoryMaker';
+import { modifyRequest } from '../utils/RequestModifier';
 
 /**
  * @module XHRLoader
@@ -44,7 +45,16 @@ function XHRLoader(cfg) {
     let instance;
 
     function load(httpRequest) {
+        if (requestModifier && requestModifier.modifyRequest) {
+            modifyRequest(httpRequest, requestModifier)
+                .then(() => request(httpRequest));
+        }
+        else {
+            request(httpRequest);
+        }
+    }
 
+    function request(httpRequest) {
         // Variables will be used in the callback functions
         const requestStartTime = new Date();
         const request = httpRequest.request;
@@ -64,7 +74,7 @@ function XHRLoader(cfg) {
             request.requestStartDate = requestStartTime;
         }
 
-        if (requestModifier) {
+        if (requestModifier && requestModifier.modifyRequestHeader) {
             xhr = requestModifier.modifyRequestHeader(xhr, {
                 url: httpRequest.url
             });
diff --git a/src/streaming/utils/RequestModifier.js b/src/streaming/utils/RequestModifier.js
index 06fbe8425d..80ff3e943f 100644
--- a/src/streaming/utils/RequestModifier.js
+++ b/src/streaming/utils/RequestModifier.js
@@ -31,6 +31,20 @@
 
 import FactoryMaker from '../../core/FactoryMaker';
 
+export function modifyRequest(httpRequest, requestModifier) {
+    const request = {
+        url: httpRequest.url,
+        method: httpRequest.method,
+        headers: Object.assign({}, httpRequest.headers),
+        credentials: httpRequest.withCredentials ? 'include' : undefined,
+    };
+
+    return Promise.resolve(requestModifier.modifyRequest(request))
+        .then(() =>
+            Object.assign(httpRequest, request, { withCredentials: request.credentials === 'include' })
+        );
+}
+
 function RequestModifier() {
 
     let instance;
@@ -40,11 +54,12 @@ function RequestModifier() {
     }
 
     // eslint-disable-next-line no-unused-vars
-    function modifyRequestHeader(request, {url}) {
+    function modifyRequestHeader(request, { url }) {
         return request;
     }
 
     instance = {
+        modifyRequest: null,
         modifyRequestURL: modifyRequestURL,
         modifyRequestHeader: modifyRequestHeader
     };