diff --git a/lib/amd/build/localstorage.min.js b/lib/amd/build/localstorage.min.js
index 1ef0f780cc4..8d0cac780df 100644
--- a/lib/amd/build/localstorage.min.js
+++ b/lib/amd/build/localstorage.min.js
@@ -1 +1 @@
-define(["core/config"],function(a){var b=!1,c="",d="",e=null,f=function(){if(a.jsrev==-1)return!1;if("undefined"==typeof window.localStorage)return!1;var b="test";try{return e=window.localStorage,null!==e&&(e.setItem(b,"1"),e.removeItem(b),!0)}catch(c){return!1}},g=function(a){return c+a},h=function(){var b=e.getItem(d);if(null===b)return void e.setItem(d,a.jsrev);var c=a.jsrev;c!=b&&(e.clear(),e.setItem(d,a.jsrev))},i=function(a){var b,c,d,e=0;if(0===a.length)return e;for(b=0,d=a.length;b.
+
+/**
+ * Simple API for set/get to sessionstorage, with cacherev expiration.
+ *
+ * Session storage will only persist for as long as the browser window
+ * stays open.
+ *
+ * See:
+ * https://developer.mozilla.org/en-US/docs/Web/API/Window/sessionStorage
+ *
+ * @module core/sessionstorage
+ * @package core
+ * @copyright 2017 Ryan Wyllie
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+define(['core/config', 'core/storagewrapper'], function(config, StorageWrapper) {
+
+ // Private functions and variables.
+ /** @var {Object} StorageWrapper - Wraps browsers sessionStorage object */
+ var storage = new StorageWrapper(window.sessionStorage);
+
+ return /** @alias module:core/sessionstorage */ {
+ /**
+ * Get a value from session storage. Remember - all values must be strings.
+ *
+ * @method get
+ * @param {string} key The cache key to check.
+ * @return {boolean|string} False if the value is not in the cache, or some other error - a string otherwise.
+ */
+ get: function(key) {
+ return storage.get(key);
+ },
+
+ /**
+ * Set a value to session storage. Remember - all values must be strings.
+ *
+ * @method set
+ * @param {string} key The cache key to set.
+ * @param {string} value The value to set.
+ * @return {boolean} False if the value can't be saved in the cache, or some other error - true otherwise.
+ */
+ set: function(key, value) {
+ return storage.set(key, value);
+ }
+
+ };
+});
diff --git a/lib/amd/src/storagewrapper.js b/lib/amd/src/storagewrapper.js
new file mode 100644
index 00000000000..7f7f3e62c06
--- /dev/null
+++ b/lib/amd/src/storagewrapper.js
@@ -0,0 +1,165 @@
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle. If not, see .
+
+/**
+ * Wrap an instance of the browser's local or session storage to handle
+ * cache expiry, key namespacing and other helpful things.
+ *
+ * @module core/storagewrapper
+ * @package core
+ * @copyright 2017 Ryan Wyllie
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+define(['core/config'], function(config) {
+
+ /**
+ * Constructor.
+ *
+ * @param {object} storage window.localStorage or window.sessionStorage
+ */
+ var Wrapper = function(storage) {
+ this.storage = storage;
+ this.supported = this.detectSupport();
+ this.hashSource = config.wwwroot + '/' + config.jsrev;
+ this.hash = this.hashString(this.hashSource);
+ this.prefix = this.hash + '/';
+ this.jsrevPrefix = this.hash + '/jsrev';
+ };
+
+ /**
+ * Check if the browser supports the type of storage.
+ *
+ * @method detectSupport
+ * @return {boolean} True if the browser supports storage.
+ */
+ Wrapper.prototype.detectSupport = function() {
+ if (config.jsrev == -1) {
+ // Disable cache if debugging.
+ return false;
+ }
+ if (typeof (this.storage) === "undefined") {
+ return false;
+ }
+ var testKey = 'test';
+ try {
+ if (this.storage === null) {
+ return false;
+ }
+ // MDL-51461 - Some browsers misreport availability of the storage
+ // so check it is actually usable.
+ this.storage.setItem(testKey, '1');
+ this.storage.removeItem(testKey);
+ return true;
+ } catch (ex) {
+ return false;
+ }
+ };
+
+ /**
+ * Add a unique prefix to all keys so multiple moodle sites do not share caches.
+ *
+ * @method prefixKey
+ * @param {string} key The cache key to prefix.
+ * @return {string} The new key
+ */
+ Wrapper.prototype.prefixKey = function(key) {
+ return this.prefix + key;
+ };
+
+ /**
+ * Check the current jsrev version and clear the cache if it has been bumped.
+ *
+ * @method validateCache
+ */
+ Wrapper.prototype.validateCache = function() {
+ var cacheVersion = this.storage.getItem(this.jsrevPrefix);
+ if (cacheVersion === null) {
+ this.storage.setItem(this.jsrevPrefix, config.jsrev);
+ return;
+ }
+ var moodleVersion = config.jsrev;
+
+ if (moodleVersion != cacheVersion) {
+ this.storage.clear();
+ this.storage.setItem(this.jsrevPrefix, config.jsrev);
+ }
+ };
+
+ /**
+ * Hash a string, used to make shorter key prefixes.
+ *
+ * @method hashString
+ * @param {String} source The string to hash
+ * @return {Number}
+ */
+ Wrapper.prototype.hashString = function(source) {
+ // From http://stackoverflow.com/questions/7616461/generate-a-hash-from-string-in-javascript-jquery.
+ /* jshint bitwise: false */
+ /* eslint no-bitwise: "off" */
+ var hash = 0;
+ var i, chr, len;
+ if (source.length === 0) {
+ return hash;
+ }
+ for (i = 0, len = source.length; i < len; i++) {
+ chr = source.charCodeAt(i);
+ hash = ((hash << 5) - hash) + chr;
+ hash |= 0; // Convert to 32bit integer
+ }
+ return hash;
+ };
+
+ /**
+ * Get a value from local storage. Remember - all values must be strings.
+ *
+ * @method get
+ * @param {string} key The cache key to check.
+ * @return {boolean|string} False if the value is not in the cache, or some other error - a string otherwise.
+ */
+ Wrapper.prototype.get = function(key) {
+ if (!this.supported) {
+ return false;
+ }
+ this.validateCache();
+ key = this.prefixKey(key);
+
+ return this.storage.getItem(key);
+ };
+
+ /**
+ * Set a value to local storage. Remember - all values must be strings.
+ *
+ * @method set
+ * @param {string} key The cache key to set.
+ * @param {string} value The value to set.
+ * @return {boolean} False if the value can't be saved in the cache, or some other error - true otherwise.
+ */
+ Wrapper.prototype.set = function(key, value) {
+ if (!this.supported) {
+ return false;
+ }
+ this.validateCache();
+ key = this.prefixKey(key);
+ // This can throw exceptions when the storage limit is reached.
+ try {
+ this.storage.setItem(key, value);
+ } catch (e) {
+ return false;
+ }
+ return true;
+ };
+
+ return Wrapper;
+});