diff --git a/.gitignore b/.gitignore
index 328093d7a09..5bc058976e7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -53,6 +53,7 @@ bootsnap-compile-cache/
 !/plugins/discourse-narrative-bot
 !/plugins/discourse-presence
 !/plugins/discourse-local-dates
+!/plugins/discourse-internet-explorer
 /plugins/*/auto_generated/
 
 /spec/fixtures/plugins/my_plugin/auto_generated
diff --git a/app/assets/javascripts/polyfills.js b/app/assets/javascripts/polyfills.js
index 9d2b88d162d..ae960cdea53 100644
--- a/app/assets/javascripts/polyfills.js
+++ b/app/assets/javascripts/polyfills.js
@@ -1,185 +1,9 @@
-// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries
-if (!Object.entries) {
-  Object.entries = function(obj) {
-    var ownProps = Object.keys(obj),
-      i = ownProps.length,
-      resArray = new Array(i); // preallocate the Array
-    while (i--) resArray[i] = [ownProps[i], obj[ownProps[i]]];
-
-    return resArray;
-  };
-}
-
-// adapted from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries
-// missing in ie only
-if (!Object.values) {
-  Object.values = function(obj) {
-    var ownProps = Object.keys(obj),
-      i = ownProps.length,
-      resArray = new Array(i); // preallocate the Array
-    while (i--) resArray[i] = obj[ownProps[i]];
-
-    return resArray;
-  };
-}
-
-// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign
-if (typeof Object.assign !== "function") {
-  // Must be writable: true, enumerable: false, configurable: true
-  Object.defineProperty(Object, "assign", {
-    value: function assign(target) {
-      // .length of function is 2
-      "use strict";
-      if (target == null) {
-        // TypeError if undefined or null
-        throw new TypeError("Cannot convert undefined or null to object");
-      }
-
-      var to = Object(target);
-
-      for (var index = 1; index < arguments.length; index++) {
-        var nextSource = arguments[index];
-
-        if (nextSource != null) {
-          // Skip over if undefined or null
-          for (var nextKey in nextSource) {
-            // Avoid bugs when hasOwnProperty is shadowed
-            if (Object.prototype.hasOwnProperty.call(nextSource, nextKey)) {
-              to[nextKey] = nextSource[nextKey];
-            }
-          }
-        }
-      }
-      return to;
-    },
-    writable: true,
-    configurable: true
-  });
-}
-
-// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes#Polyfill
 /* eslint-disable */
-if (!Array.prototype.includes) {
-  Object.defineProperty(Array.prototype, "includes", {
-    value: function(searchElement, fromIndex) {
-      if (this == null) {
-        throw new TypeError('"this" is null or not defined');
-      }
 
-      // 1. Let O be ? ToObject(this value).
-      var o = Object(this);
-
-      // 2. Let len be ? ToLength(? Get(O, "length")).
-      var len = o.length >>> 0;
-
-      // 3. If len is 0, return false.
-      if (len === 0) {
-        return false;
-      }
-
-      // 4. Let n be ? ToInteger(fromIndex).
-      //    (If fromIndex is undefined, this step produces the value 0.)
-      var n = fromIndex | 0;
-
-      // 5. If n ≥ 0, then
-      //  a. Let k be n.
-      // 6. Else n < 0,
-      //  a. Let k be len + n.
-      //  b. If k < 0, let k be 0.
-      var k = Math.max(n >= 0 ? n : len - Math.abs(n), 0);
-
-      function sameValueZero(x, y) {
-        return (
-          x === y ||
-          (typeof x === "number" &&
-            typeof y === "number" &&
-            isNaN(x) &&
-            isNaN(y))
-        );
-      }
-
-      // 7. Repeat, while k < len
-      while (k < len) {
-        // a. Let elementK be the result of ? Get(O, ! ToString(k)).
-        // b. If SameValueZero(searchElement, elementK) is true, return true.
-        if (sameValueZero(o[k], searchElement)) {
-          return true;
-        }
-        // c. Increase k by 1.
-        k++;
-      }
-
-      // 8. Return false
-      return false;
-    }
-  });
-}
-
-// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/includes#Polyfill
-if (!String.prototype.includes) {
-  Object.defineProperty(String.prototype, "includes", {
-    value: function(search, start) {
-      if (typeof start !== "number") {
-        start = 0;
-      }
-
-      if (start + search.length > this.length) {
-        return false;
-      } else {
-        return this.indexOf(search, start) !== -1;
-      }
-    }
-  });
-}
-
-// https://tc39.github.io/ecma262/#sec-array.prototype.find
-if (!Array.prototype.find) {
-  Object.defineProperty(Array.prototype, "find", {
-    value: function(predicate) {
-      // 1. Let O be ? ToObject(this value).
-      if (this == null) {
-        throw new TypeError('"this" is null or not defined');
-      }
-
-      var o = Object(this);
-
-      // 2. Let len be ? ToLength(? Get(O, "length")).
-      var len = o.length >>> 0;
-
-      // 3. If IsCallable(predicate) is false, throw a TypeError exception.
-      if (typeof predicate !== "function") {
-        throw new TypeError("predicate must be a function");
-      }
-
-      // 4. If thisArg was supplied, let T be thisArg; else let T be undefined.
-      var thisArg = arguments[1];
-
-      // 5. Let k be 0.
-      var k = 0;
-
-      // 6. Repeat, while k < len
-      while (k < len) {
-        // a. Let Pk be ! ToString(k).
-        // b. Let kValue be ? Get(O, Pk).
-        // c. Let testResult be ToBoolean(? Call(predicate, T, « kValue, k, O »)).
-        // d. If testResult is true, return kValue.
-        var kValue = o[k];
-        if (predicate.call(thisArg, kValue, k, o)) {
-          return kValue;
-        }
-        // e. Increase k by 1.
-        k++;
-      }
-
-      // 7. Return undefined.
-      return undefined;
-    },
-    configurable: true,
-    writable: true
-  });
-}
+// Any IE only polyfill should be moved in discourse-internet-explorer plugin
 
 // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/flags#Polyfill
+// IE and EDGE
 if (RegExp.prototype.flags === undefined) {
   Object.defineProperty(RegExp.prototype, "flags", {
     configurable: true,
@@ -189,181 +13,4 @@ if (RegExp.prototype.flags === undefined) {
   });
 }
 
-// https://github.com/uxitten/polyfill/blob/master/string.polyfill.js
-// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/padStart
-if (!String.prototype.padStart) {
-  String.prototype.padStart = function padStart(targetLength, padString) {
-    targetLength = targetLength >> 0; //truncate if number, or convert non-number to 0;
-    padString = String(typeof padString !== "undefined" ? padString : " ");
-    if (this.length >= targetLength) {
-      return String(this);
-    } else {
-      targetLength = targetLength - this.length;
-      if (targetLength > padString.length) {
-        padString += padString.repeat(targetLength / padString.length); //append to original to ensure we are longer than needed
-      }
-      return padString.slice(0, targetLength) + String(this);
-    }
-  };
-}
-
-// https://github.com/uxitten/polyfill/blob/master/string.polyfill.js
-// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/padEnd
-if (!String.prototype.padEnd) {
-  String.prototype.padEnd = function padEnd(targetLength, padString) {
-    targetLength = targetLength >> 0; //floor if number or convert non-number to 0;
-    padString = String(typeof padString !== "undefined" ? padString : " ");
-    if (this.length > targetLength) {
-      return String(this);
-    } else {
-      targetLength = targetLength - this.length;
-      if (targetLength > padString.length) {
-        padString += padString.repeat(targetLength / padString.length); //append to original to ensure we are longer than needed
-      }
-      return String(this) + padString.slice(0, targetLength);
-    }
-  };
-}
-
-// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/from
-// Production steps of ECMA-262, Edition 6, 22.1.2.1
-if (!Array.from) {
-  Array.from = (function() {
-    var toStr = Object.prototype.toString;
-    var isCallable = function(fn) {
-      return typeof fn === "function" || toStr.call(fn) === "[object Function]";
-    };
-    var toInteger = function(value) {
-      var number = Number(value);
-      if (isNaN(number)) {
-        return 0;
-      }
-      if (number === 0 || !isFinite(number)) {
-        return number;
-      }
-      return (number > 0 ? 1 : -1) * Math.floor(Math.abs(number));
-    };
-    var maxSafeInteger = Math.pow(2, 53) - 1;
-    var toLength = function(value) {
-      var len = toInteger(value);
-      return Math.min(Math.max(len, 0), maxSafeInteger);
-    };
-
-    // The length property of the from method is 1.
-    return function from(arrayLike /*, mapFn, thisArg */) {
-      // 1. Let C be the this value.
-      var C = this;
-
-      // 2. Let items be ToObject(arrayLike).
-      var items = Object(arrayLike);
-
-      // 3. ReturnIfAbrupt(items).
-      if (arrayLike == null) {
-        throw new TypeError(
-          "Array.from requires an array-like object - not null or undefined"
-        );
-      }
-
-      // 4. If mapfn is undefined, then let mapping be false.
-      var mapFn = arguments.length > 1 ? arguments[1] : void undefined;
-      var T;
-      if (typeof mapFn !== "undefined") {
-        // 5. else
-        // 5. a If IsCallable(mapfn) is false, throw a TypeError exception.
-        if (!isCallable(mapFn)) {
-          throw new TypeError(
-            "Array.from: when provided, the second argument must be a function"
-          );
-        }
-
-        // 5. b. If thisArg was supplied, let T be thisArg; else let T be undefined.
-        if (arguments.length > 2) {
-          T = arguments[2];
-        }
-      }
-
-      // 10. Let lenValue be Get(items, "length").
-      // 11. Let len be ToLength(lenValue).
-      var len = toLength(items.length);
-
-      // 13. If IsConstructor(C) is true, then
-      // 13. a. Let A be the result of calling the [[Construct]] internal method
-      // of C with an argument list containing the single item len.
-      // 14. a. Else, Let A be ArrayCreate(len).
-      var A = isCallable(C) ? Object(new C(len)) : new Array(len);
-
-      // 16. Let k be 0.
-      var k = 0;
-      // 17. Repeat, while k < len… (also steps a - h)
-      var kValue;
-      while (k < len) {
-        kValue = items[k];
-        if (mapFn) {
-          A[k] =
-            typeof T === "undefined"
-              ? mapFn(kValue, k)
-              : mapFn.call(T, kValue, k);
-        } else {
-          A[k] = kValue;
-        }
-        k += 1;
-      }
-      // 18. Let putStatus be Put(A, "length", len, true).
-      A.length = len;
-      // 20. Return A.
-      return A;
-    };
-  })();
-}
-
-// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat#Polyfill
-if (!String.prototype.repeat) {
-  String.prototype.repeat = function(count) {
-    "use strict";
-    if (this == null)
-      throw new TypeError("can't convert " + this + " to object");
-
-    var str = "" + this;
-    // To convert string to integer.
-    count = +count;
-    // Check NaN
-    if (count != count) count = 0;
-
-    if (count < 0) throw new RangeError("repeat count must be non-negative");
-
-    if (count == Infinity)
-      throw new RangeError("repeat count must be less than infinity");
-
-    count = Math.floor(count);
-    if (str.length == 0 || count == 0) return "";
-
-    // Ensuring count is a 31-bit integer allows us to heavily optimize the
-    // main part. But anyway, most current (August 2014) browsers can't handle
-    // strings 1 << 28 chars or longer, so:
-    if (str.length * count >= 1 << 28)
-      throw new RangeError(
-        "repeat count must not overflow maximum string size"
-      );
-
-    var maxCount = str.length * count;
-    count = Math.floor(Math.log(count) / Math.log(2));
-    while (count) {
-      str += str;
-      count--;
-    }
-    str += str.substring(0, maxCount - str.length);
-    return str;
-  };
-}
-
-// https://developer.mozilla.org/fr/docs/Web/API/NodeList/forEach
-if (window.NodeList && !NodeList.prototype.forEach) {
-  NodeList.prototype.forEach = function(callback, thisArg) {
-    thisArg = thisArg || window;
-    for (var i = 0; i < this.length; i++) {
-      callback.call(thisArg, this[i], i, this);
-    }
-  };
-}
-
 /* eslint-enable */
diff --git a/app/assets/stylesheets/common/admin/staff_logs.scss b/app/assets/stylesheets/common/admin/staff_logs.scss
index 058fcb4543d..c6839df88d1 100644
--- a/app/assets/stylesheets/common/admin/staff_logs.scss
+++ b/app/assets/stylesheets/common/admin/staff_logs.scss
@@ -76,46 +76,6 @@
     }
   }
 
-  //IE11 Support
-  @media screen and (max-width: 767px) {
-    table.staff-logs tr {
-      display: -ms-grid;
-      -ms-grid-columns: 1fr 1fr 1fr 0.5fr;
-      -ms-grid-rows: auto auto;
-      td {
-        display: -ms-grid;
-        &.staff-users {
-          -ms-grid-row: 1;
-          -ms-grid-column: 1;
-          -ms-grid-column-span: 2;
-        }
-        &.created-at {
-          -ms-grid-row: 1;
-          -ms-grid-column: 4;
-        }
-        &.action {
-          -ms-grid-row: 2;
-          -ms-grid-column: 1;
-        }
-        &.subject {
-          -ms-grid-row: 2;
-          -ms-grid-column: 2;
-          -ms-grid-column-span: 3;
-        }
-        &.details {
-          -ms-grid-row: 3;
-          -ms-grid-column: 1;
-          -ms-grid-column-span: 3;
-        }
-        &.context {
-          -ms-grid-row: 4;
-          -ms-grid-column: 1;
-          -ms-grid-column-span: 3;
-        }
-      }
-    }
-  }
-
   @include breakpoint(mobile-extra-large) {
     table.staff-logs tr {
       grid-template-columns: 1fr 1fr 0.5fr;
diff --git a/lib/plugin/instance.rb b/lib/plugin/instance.rb
index 92db214d798..8723cf2d9f1 100644
--- a/lib/plugin/instance.rb
+++ b/lib/plugin/instance.rb
@@ -84,7 +84,7 @@ class Plugin::Instance
 
   def register_anonymous_cache_key(key, &block)
     key_method = "key_#{key}"
-    add_to_class(Middleware::AnonymousCache, key_method, &block)
+    add_to_class(Middleware::AnonymousCache::Helper, key_method, &block)
     Middleware::AnonymousCache.cache_key_segments[key] = key_method
     Middleware::AnonymousCache.compile_key_builder
   end
diff --git a/lib/plugin/metadata.rb b/lib/plugin/metadata.rb
index da74e43a11c..c626d711ca2 100644
--- a/lib/plugin/metadata.rb
+++ b/lib/plugin/metadata.rb
@@ -72,7 +72,8 @@ class Plugin::Metadata
     "discourse-rss-polling",
     "docker_manager",
     "lazy-yt",
-    "poll"
+    "poll",
+    "discourse-internet-explorer"
   ])
 
   FIELDS ||= [:name, :about, :version, :authors, :url, :required_version]
diff --git a/plugins/discourse-internet-explorer/assets/stylesheets/ie.scss b/plugins/discourse-internet-explorer/assets/stylesheets/ie.scss
new file mode 100644
index 00000000000..23b125e2191
--- /dev/null
+++ b/plugins/discourse-internet-explorer/assets/stylesheets/ie.scss
@@ -0,0 +1,38 @@
+@media screen and (max-width: 767px) {
+  table.staff-logs tr {
+    display: -ms-grid;
+    -ms-grid-columns: 1fr 1fr 1fr 0.5fr;
+    -ms-grid-rows: auto auto;
+    td {
+      display: -ms-grid;
+      &.staff-users {
+        -ms-grid-row: 1;
+        -ms-grid-column: 1;
+        -ms-grid-column-span: 2;
+      }
+      &.created-at {
+        -ms-grid-row: 1;
+        -ms-grid-column: 4;
+      }
+      &.action {
+        -ms-grid-row: 2;
+        -ms-grid-column: 1;
+      }
+      &.subject {
+        -ms-grid-row: 2;
+        -ms-grid-column: 2;
+        -ms-grid-column-span: 3;
+      }
+      &.details {
+        -ms-grid-row: 3;
+        -ms-grid-column: 1;
+        -ms-grid-column-span: 3;
+      }
+      &.context {
+        -ms-grid-row: 4;
+        -ms-grid-column: 1;
+        -ms-grid-column-span: 3;
+      }
+    }
+  }
+}
diff --git a/plugins/discourse-internet-explorer/config/locales/server.en.yml b/plugins/discourse-internet-explorer/config/locales/server.en.yml
new file mode 100644
index 00000000000..935cbc4b981
--- /dev/null
+++ b/plugins/discourse-internet-explorer/config/locales/server.en.yml
@@ -0,0 +1,3 @@
+en:
+  site_settings:
+    discourse_internet_explorer_enabled: "Internet Explorer support"
diff --git a/plugins/discourse-internet-explorer/config/settings.yml b/plugins/discourse-internet-explorer/config/settings.yml
new file mode 100644
index 00000000000..23f2be3a202
--- /dev/null
+++ b/plugins/discourse-internet-explorer/config/settings.yml
@@ -0,0 +1,3 @@
+plugins:
+  discourse_internet_explorer_enabled:
+    default: true
diff --git a/plugins/discourse-internet-explorer/plugin.rb b/plugins/discourse-internet-explorer/plugin.rb
new file mode 100644
index 00000000000..5f80a79ad3b
--- /dev/null
+++ b/plugins/discourse-internet-explorer/plugin.rb
@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+# name: discourse-internet-explorer
+# about: Attempts to provide backward support for internt explorer
+# version: 1.0
+# authors: Joffrey Jaffeux, David Taylor, Daniel Waterworth, Robin Ward
+# url: https://github.com/discourse/discourse/tree/master/plugins/discourse-internet-explorer
+
+enabled_site_setting :discourse_internet_explorer_enabled
+hide_plugin if self.respond_to?(:hide_plugin)
+
+register_asset 'stylesheets/ie.scss'
+
+after_initialize do
+
+  # Conditionally load the stylesheet. There is unfortunately no easy way to do this via
+  # Plugin API.
+  reloadable_patch do |plugin|
+    ApplicationHelper.module_eval do
+      alias_method :previous_discourse_stylesheet_link_tag, :discourse_stylesheet_link_tag
+      def discourse_stylesheet_link_tag(name, opts = {})
+
+        if name == 'discourse-internet-explorer'
+          return unless SiteSetting.discourse_internet_explorer_enabled?
+          return unless request.env['HTTP_USER_AGENT'] =~ /MSIE|Trident/
+        end
+
+        previous_discourse_stylesheet_link_tag(name, opts)
+      end
+    end
+  end
+
+  register_anonymous_cache_key(:ie) do
+    unless defined?(@is_ie)
+      session = @env[self.class::RACK_SESSION]
+      # don't initialize params until later
+      # otherwise you get a broken params on the request
+      params = {}
+
+      @is_ie = BrowserDetection.browser(@env[self.class::USER_AGENT]) == :ie
+    end
+
+    @is_ie
+  end
+
+  # not using patch on preload_script as js is fine and we need this file
+  # to be loaded before other files
+  register_html_builder('server:before-script-load') do |controller|
+    if BrowserDetection.browser(controller.request.env['HTTP_USER_AGENT']) == :ie
+      path = controller.helpers.script_asset_path('/plugins/discourse-internet-explorer/js/ie')
+
+      <<~JAVASCRIPT
+        <script src="#{path}"></script>
+      JAVASCRIPT
+    end
+  end
+end
diff --git a/plugins/discourse-internet-explorer/public/js/ie.js b/plugins/discourse-internet-explorer/public/js/ie.js
new file mode 100644
index 00000000000..5d252b97064
--- /dev/null
+++ b/plugins/discourse-internet-explorer/public/js/ie.js
@@ -0,0 +1,347 @@
+/* eslint-disable */
+
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries
+if (!Object.values) {
+  Object.values = function(obj) {
+    var ownProps = Object.keys(obj),
+      i = ownProps.length,
+      resArray = new Array(i); // preallocate the Array
+    while (i--) resArray[i] = obj[ownProps[i]];
+
+    return resArray;
+  };
+}
+
+// https://developer.mozilla.org/fr/docs/Web/API/NodeList/forEach
+if (window.NodeList && !NodeList.prototype.forEach) {
+  NodeList.prototype.forEach = function(callback, thisArg) {
+    thisArg = thisArg || window;
+    for (var i = 0; i < this.length; i++) {
+      callback.call(thisArg, this[i], i, this);
+    }
+  };
+}
+
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes#Polyfill
+if (!Array.prototype.includes) {
+  Object.defineProperty(Array.prototype, "includes", {
+    value: function(searchElement, fromIndex) {
+      if (this == null) {
+        throw new TypeError('"this" is null or not defined');
+      }
+
+      // 1. Let O be ? ToObject(this value).
+      var o = Object(this);
+
+      // 2. Let len be ? ToLength(? Get(O, "length")).
+      var len = o.length >>> 0;
+
+      // 3. If len is 0, return false.
+      if (len === 0) {
+        return false;
+      }
+
+      // 4. Let n be ? ToInteger(fromIndex).
+      //    (If fromIndex is undefined, this step produces the value 0.)
+      var n = fromIndex | 0;
+
+      // 5. If n ≥ 0, then
+      //  a. Let k be n.
+      // 6. Else n < 0,
+      //  a. Let k be len + n.
+      //  b. If k < 0, let k be 0.
+      var k = Math.max(n >= 0 ? n : len - Math.abs(n), 0);
+
+      function sameValueZero(x, y) {
+        return (
+          x === y ||
+          (typeof x === "number" &&
+            typeof y === "number" &&
+            isNaN(x) &&
+            isNaN(y))
+        );
+      }
+
+      // 7. Repeat, while k < len
+      while (k < len) {
+        // a. Let elementK be the result of ? Get(O, ! ToString(k)).
+        // b. If SameValueZero(searchElement, elementK) is true, return true.
+        if (sameValueZero(o[k], searchElement)) {
+          return true;
+        }
+        // c. Increase k by 1.
+        k++;
+      }
+
+      // 8. Return false
+      return false;
+    }
+  });
+}
+
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/includes#Polyfill
+if (!String.prototype.includes) {
+  Object.defineProperty(String.prototype, "includes", {
+    value: function(search, start) {
+      if (typeof start !== "number") {
+        start = 0;
+      }
+
+      if (start + search.length > this.length) {
+        return false;
+      } else {
+        return this.indexOf(search, start) !== -1;
+      }
+    }
+  });
+}
+
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find
+if (!Array.prototype.find) {
+  Object.defineProperty(Array.prototype, "find", {
+    value: function(predicate) {
+      // 1. Let O be ? ToObject(this value).
+      if (this == null) {
+        throw new TypeError('"this" is null or not defined');
+      }
+
+      var o = Object(this);
+
+      // 2. Let len be ? ToLength(? Get(O, "length")).
+      var len = o.length >>> 0;
+
+      // 3. If IsCallable(predicate) is false, throw a TypeError exception.
+      if (typeof predicate !== "function") {
+        throw new TypeError("predicate must be a function");
+      }
+
+      // 4. If thisArg was supplied, let T be thisArg; else let T be undefined.
+      var thisArg = arguments[1];
+
+      // 5. Let k be 0.
+      var k = 0;
+
+      // 6. Repeat, while k < len
+      while (k < len) {
+        // a. Let Pk be ! ToString(k).
+        // b. Let kValue be ? Get(O, Pk).
+        // c. Let testResult be ToBoolean(? Call(predicate, T, « kValue, k, O »)).
+        // d. If testResult is true, return kValue.
+        var kValue = o[k];
+        if (predicate.call(thisArg, kValue, k, o)) {
+          return kValue;
+        }
+        // e. Increase k by 1.
+        k++;
+      }
+
+      // 7. Return undefined.
+      return undefined;
+    },
+    configurable: true,
+    writable: true
+  });
+}
+
+// https://github.com/uxitten/polyfill/blob/master/string.polyfill.js
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/padStart
+if (!String.prototype.padStart) {
+  String.prototype.padStart = function padStart(targetLength, padString) {
+    targetLength = targetLength >> 0; //truncate if number, or convert non-number to 0;
+    padString = String(typeof padString !== "undefined" ? padString : " ");
+    if (this.length >= targetLength) {
+      return String(this);
+    } else {
+      targetLength = targetLength - this.length;
+      if (targetLength > padString.length) {
+        padString += padString.repeat(targetLength / padString.length); //append to original to ensure we are longer than needed
+      }
+      return padString.slice(0, targetLength) + String(this);
+    }
+  };
+}
+
+// https://github.com/uxitten/polyfill/blob/master/string.polyfill.js
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/padEnd
+if (!String.prototype.padEnd) {
+  String.prototype.padEnd = function padEnd(targetLength, padString) {
+    targetLength = targetLength >> 0; //floor if number or convert non-number to 0;
+    padString = String(typeof padString !== "undefined" ? padString : " ");
+    if (this.length > targetLength) {
+      return String(this);
+    } else {
+      targetLength = targetLength - this.length;
+      if (targetLength > padString.length) {
+        padString += padString.repeat(targetLength / padString.length); //append to original to ensure we are longer than needed
+      }
+      return String(this) + padString.slice(0, targetLength);
+    }
+  };
+}
+
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/from
+// Production steps of ECMA-262, Edition 6, 22.1.2.1
+if (!Array.from) {
+  Array.from = (function() {
+    var toStr = Object.prototype.toString;
+    var isCallable = function(fn) {
+      return typeof fn === "function" || toStr.call(fn) === "[object Function]";
+    };
+    var toInteger = function(value) {
+      var number = Number(value);
+      if (isNaN(number)) {
+        return 0;
+      }
+      if (number === 0 || !isFinite(number)) {
+        return number;
+      }
+      return (number > 0 ? 1 : -1) * Math.floor(Math.abs(number));
+    };
+    var maxSafeInteger = Math.pow(2, 53) - 1;
+    var toLength = function(value) {
+      var len = toInteger(value);
+      return Math.min(Math.max(len, 0), maxSafeInteger);
+    };
+
+    // The length property of the from method is 1.
+    return function from(arrayLike /*, mapFn, thisArg */) {
+      // 1. Let C be the this value.
+      var C = this;
+
+      // 2. Let items be ToObject(arrayLike).
+      var items = Object(arrayLike);
+
+      // 3. ReturnIfAbrupt(items).
+      if (arrayLike == null) {
+        throw new TypeError(
+          "Array.from requires an array-like object - not null or undefined"
+        );
+      }
+
+      // 4. If mapfn is undefined, then let mapping be false.
+      var mapFn = arguments.length > 1 ? arguments[1] : void undefined;
+      var T;
+      if (typeof mapFn !== "undefined") {
+        // 5. else
+        // 5. a If IsCallable(mapfn) is false, throw a TypeError exception.
+        if (!isCallable(mapFn)) {
+          throw new TypeError(
+            "Array.from: when provided, the second argument must be a function"
+          );
+        }
+
+        // 5. b. If thisArg was supplied, let T be thisArg; else let T be undefined.
+        if (arguments.length > 2) {
+          T = arguments[2];
+        }
+      }
+
+      // 10. Let lenValue be Get(items, "length").
+      // 11. Let len be ToLength(lenValue).
+      var len = toLength(items.length);
+
+      // 13. If IsConstructor(C) is true, then
+      // 13. a. Let A be the result of calling the [[Construct]] internal method
+      // of C with an argument list containing the single item len.
+      // 14. a. Else, Let A be ArrayCreate(len).
+      var A = isCallable(C) ? Object(new C(len)) : new Array(len);
+
+      // 16. Let k be 0.
+      var k = 0;
+      // 17. Repeat, while k < len… (also steps a - h)
+      var kValue;
+      while (k < len) {
+        kValue = items[k];
+        if (mapFn) {
+          A[k] =
+            typeof T === "undefined"
+              ? mapFn(kValue, k)
+              : mapFn.call(T, kValue, k);
+        } else {
+          A[k] = kValue;
+        }
+        k += 1;
+      }
+      // 18. Let putStatus be Put(A, "length", len, true).
+      A.length = len;
+      // 20. Return A.
+      return A;
+    };
+  })();
+}
+
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign
+if (typeof Object.assign !== "function") {
+  // Must be writable: true, enumerable: false, configurable: true
+  Object.defineProperty(Object, "assign", {
+    value: function assign(target) {
+      // .length of function is 2
+      "use strict";
+      if (target == null) {
+        // TypeError if undefined or null
+        throw new TypeError("Cannot convert undefined or null to object");
+      }
+
+      var to = Object(target);
+
+      for (var index = 1; index < arguments.length; index++) {
+        var nextSource = arguments[index];
+
+        if (nextSource != null) {
+          // Skip over if undefined or null
+          for (var nextKey in nextSource) {
+            // Avoid bugs when hasOwnProperty is shadowed
+            if (Object.prototype.hasOwnProperty.call(nextSource, nextKey)) {
+              to[nextKey] = nextSource[nextKey];
+            }
+          }
+        }
+      }
+      return to;
+    },
+    writable: true,
+    configurable: true
+  });
+}
+
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat#Polyfill
+if (!String.prototype.repeat) {
+  String.prototype.repeat = function(count) {
+    "use strict";
+    if (this == null)
+      throw new TypeError("can't convert " + this + " to object");
+
+    var str = "" + this;
+    // To convert string to integer.
+    count = +count;
+    // Check NaN
+    if (count != count) count = 0;
+
+    if (count < 0) throw new RangeError("repeat count must be non-negative");
+
+    if (count == Infinity)
+      throw new RangeError("repeat count must be less than infinity");
+
+    count = Math.floor(count);
+    if (str.length == 0 || count == 0) return "";
+
+    // Ensuring count is a 31-bit integer allows us to heavily optimize the
+    // main part. But anyway, most current (August 2014) browsers can't handle
+    // strings 1 << 28 chars or longer, so:
+    if (str.length * count >= 1 << 28)
+      throw new RangeError(
+        "repeat count must not overflow maximum string size"
+      );
+
+    var maxCount = str.length * count;
+    count = Math.floor(Math.log(count) / Math.log(2));
+    while (count) {
+      str += str;
+      count--;
+    }
+    str += str.substring(0, maxCount - str.length);
+    return str;
+  };
+}
+
+/* eslint-enable */
diff --git a/plugins/discourse-internet-explorer/spec/middleware/anonymous_cache_spec.rb b/plugins/discourse-internet-explorer/spec/middleware/anonymous_cache_spec.rb
new file mode 100644
index 00000000000..ccd725e9dac
--- /dev/null
+++ b/plugins/discourse-internet-explorer/spec/middleware/anonymous_cache_spec.rb
@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+describe Middleware::AnonymousCache::Helper do
+  def env(opts = {})
+    {
+      "HTTP_HOST" => "http://test.com",
+      "REQUEST_URI" => "/path?bla=1",
+      "REQUEST_METHOD" => "GET",
+      "rack.input" => ""
+    }.merge(opts)
+  end
+
+  def new_helper(opts = {})
+    Middleware::AnonymousCache::Helper.new(env(opts))
+  end
+
+  it "includes ie in cache key" do
+    helper = new_helper
+    expect(helper.cache_key).to include("ie=false")
+
+    helper = new_helper("HTTP_USER_AGENT" => "Mozilla/5.0 (Windows NT 6.3; Trident/7.0; rv:11.0) like Gecko")
+    expect(helper.cache_key).to include("ie=true")
+  end
+end
diff --git a/plugins/discourse-internet-explorer/spec/requests/bootstrap_request_spec.rb b/plugins/discourse-internet-explorer/spec/requests/bootstrap_request_spec.rb
new file mode 100644
index 00000000000..bf31a251c2b
--- /dev/null
+++ b/plugins/discourse-internet-explorer/spec/requests/bootstrap_request_spec.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe 'Bootstrapping the Discourse App' do
+  let(:ie_agent) { "Mozilla/5.0 (Windows NT 6.3; Trident/7.0; rv:11.0) like Gecko" }
+
+  context "when disabled" do
+    before do
+      SiteSetting.discourse_internet_explorer_enabled = false
+    end
+
+    it "does not include the IE stylesheet or Javascript" do
+      get "/categories", headers: { "HTTP_USER_AGENT" => ie_agent }
+      expect(response.body).not_to match(/discourse-internet-explorer\/js\/ie.js/)
+      expect(response.body).not_to match(/stylesheets\/discourse-internet-explorer/)
+    end
+  end
+
+  context "when enabled" do
+    before do
+      SiteSetting.discourse_internet_explorer_enabled = true
+    end
+
+    it "includes the IE js and css" do
+      get "/categories", headers: { "HTTP_USER_AGENT" => ie_agent }
+      expect(response.body).to match(/discourse-internet-explorer\/js\/ie.js/)
+      expect(response.body).to match(/stylesheets\/discourse-internet-explorer/)
+    end
+
+    it "doesn't include IE stuff for non-IE browsers" do
+      get "/categories", headers: { "HTTP_USER_AGENT" => "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.70 Safari/537.36" }
+      expect(response.body).not_to match(/discourse-internet-explorer\/js\/ie.js/)
+      expect(response.body).not_to match(/stylesheets\/discourse-internet-explorer/)
+    end
+  end
+end