diff --git a/src/Resource.js b/src/Resource.js
index 91f3490..ead87f0 100644
--- a/src/Resource.js
+++ b/src/Resource.js
@@ -91,6 +91,14 @@ export default class Resource {
          */
         this.url = url;
 
+        /**
+         * The extension used to load this resource.
+         *
+         * @member {string}
+         * @readonly
+         */
+        this.extension = this._getExtension();
+
         /**
          * The data that was loaded by the resource.
          *
@@ -815,7 +823,7 @@ export default class Resource {
      * @return {Resource.XHR_RESPONSE_TYPE} The responseType to use.
      */
     _determineXhrType() {
-        return Resource._xhrTypeMap[this._getExtension()] || Resource.XHR_RESPONSE_TYPE.TEXT;
+        return Resource._xhrTypeMap[this.extension] || Resource.XHR_RESPONSE_TYPE.TEXT;
     }
 
     /**
@@ -826,7 +834,7 @@ export default class Resource {
      * @return {Resource.LOAD_TYPE} The loadType to use.
      */
     _determineLoadType() {
-        return Resource._loadTypeMap[this._getExtension()] || Resource.LOAD_TYPE.XHR;
+        return Resource._loadTypeMap[this.extension] || Resource.LOAD_TYPE.XHR;
     }
 
     /**