diff --git a/fetch/nosniff/parsing-nosniff.html b/fetch/nosniff/parsing-nosniff.html
deleted file mode 100644
index 10c5cadfcaadd8..00000000000000
--- a/fetch/nosniff/parsing-nosniff.html
+++ /dev/null
@@ -1,28 +0,0 @@
-<script src=/resources/testharness.js></script>
-<script src=/resources/testharnessreport.js></script>
-<div id=log></div>
-<script>
-  var fails = ["first", "uppercase"],
-      passes = ["last", "quoted", "quoted-single", "no-x"]
-
-  fails.forEach(function(urlpart) {
-    async_test(function(t) {
-      var script = document.createElement("script")
-      script.onerror = t.step_func_done(function(){})
-      script.onload = t.unreached_func("Unexpected load event")
-      script.src = "resources/nosniff-" + urlpart + ".asis"
-      document.body.appendChild(script)
-    }, "URL query: " + urlpart)
-  })
-
-  passes.forEach(function(urlpart) {
-    async_test(function(t) {
-      var script = document.createElement("script")
-      script.onerror = t.unreached_func("Unexpected error event")
-      script.onload = t.step_func_done(function(){})
-      script.src = "resources/nosniff-" + urlpart + ".asis"
-      document.body.appendChild(script)
-    }, "URL query: " + urlpart)
-  })
-
-</script>
diff --git a/fetch/nosniff/parsing-nosniff.window.js b/fetch/nosniff/parsing-nosniff.window.js
new file mode 100644
index 00000000000000..043e659127b2c4
--- /dev/null
+++ b/fetch/nosniff/parsing-nosniff.window.js
@@ -0,0 +1,24 @@
+promise_test(() => fetch("resources/x-content-type-options.json").then(res => res.json()).then(runTests), "Loading JSON…");
+
+function runTests(allTestData) {
+  for (let i = 0; i < allTestData.length; i++) {
+    const testData = allTestData[i],
+          input = encodeURIComponent(testData.input);
+    async_test(t => {
+      const script = document.createElement("script");
+      t.add_cleanup(() => script.remove());
+      // A <script> element loading a classic script does not care about the MIME type, unless
+      // X-Content-Type-Options: nosniff is specified, in which case a JavaScript MIME type is
+      // enforced, which x/x is not.
+      if (testData.nosniff) {
+        script.onerror = t.step_func_done();
+        script.onload = t.unreached_func("Script should not have loaded");
+      } else {
+        script.onerror = t.unreached_func("Script should have loaded");
+        script.onload = t.step_func_done();
+      }
+      script.src = "resources/nosniff.py?nosniff=" + input;
+      document.body.appendChild(script);
+    }, input);
+  }
+}
diff --git a/fetch/nosniff/resources/nosniff-first.asis b/fetch/nosniff/resources/nosniff-first.asis
deleted file mode 100644
index bccc53eef8acd4..00000000000000
--- a/fetch/nosniff/resources/nosniff-first.asis
+++ /dev/null
@@ -1,7 +0,0 @@
-HTTP/1.1 200 YOU HAVE NO POWER HERE
-Content-Length: 22
-Content-Type: x/x
-X-Content-Type-options: nosniff
-X-Content-Type-Options: no
-
-// nothing to see here
diff --git a/fetch/nosniff/resources/nosniff-last.asis b/fetch/nosniff/resources/nosniff-last.asis
deleted file mode 100644
index e3de0733e4fb6f..00000000000000
--- a/fetch/nosniff/resources/nosniff-last.asis
+++ /dev/null
@@ -1,7 +0,0 @@
-HTTP/1.1 200 YOU HAVE NO POWER HERE
-Content-Length: 22
-Content-Type: x/x
-X-Content-Type-Options: no
-X-Content-Type-options: nosniff
-
-// nothing to see here
diff --git a/fetch/nosniff/resources/nosniff-no-x.asis b/fetch/nosniff/resources/nosniff-no-x.asis
deleted file mode 100644
index 329d0f72143a4e..00000000000000
--- a/fetch/nosniff/resources/nosniff-no-x.asis
+++ /dev/null
@@ -1,6 +0,0 @@
-HTTP/1.1 200 YOU HAVE NO POWER HERE
-Content-Length: 22
-Content-Type: x/x
-Content-Type-Options: nosniff
-
-// nothing to see here
diff --git a/fetch/nosniff/resources/nosniff-quoted-single.asis b/fetch/nosniff/resources/nosniff-quoted-single.asis
deleted file mode 100644
index 501f18999d0741..00000000000000
--- a/fetch/nosniff/resources/nosniff-quoted-single.asis
+++ /dev/null
@@ -1,6 +0,0 @@
-HTTP/1.1 200 YOU HAVE NO POWER HERE
-Content-Length: 22
-Content-Type: x/x
-X-Content-Type-Options: 'NosniFF'
-
-// nothing to see here
diff --git a/fetch/nosniff/resources/nosniff-quoted.asis b/fetch/nosniff/resources/nosniff-quoted.asis
deleted file mode 100644
index c6de62b689e2fd..00000000000000
--- a/fetch/nosniff/resources/nosniff-quoted.asis
+++ /dev/null
@@ -1,6 +0,0 @@
-HTTP/1.1 200 YOU HAVE NO POWER HERE
-Content-Length: 22
-Content-Type: x/x
-X-Content-Type-Options: "nosniFF"
-
-// nothing to see here
diff --git a/fetch/nosniff/resources/nosniff-uppercase.asis b/fetch/nosniff/resources/nosniff-uppercase.asis
deleted file mode 100644
index 8097fddce106ab..00000000000000
--- a/fetch/nosniff/resources/nosniff-uppercase.asis
+++ /dev/null
@@ -1,6 +0,0 @@
-HTTP/1.1 200 YOU HAVE NO POWER HERE
-Content-Length: 22
-Content-Type: x/x
-X-Content-Type-Options: NOSNIFF
-
-// nothing to see here
diff --git a/fetch/nosniff/resources/nosniff.py b/fetch/nosniff/resources/nosniff.py
new file mode 100644
index 00000000000000..9b59d35b925ef4
--- /dev/null
+++ b/fetch/nosniff/resources/nosniff.py
@@ -0,0 +1,10 @@
+def main(request, response):
+    response.add_required_headers = False
+    output =  "HTTP/1.1 220 YOU HAVE NO POWER HERE\r\n"
+    output += "Content-Length: 22\r\n"
+    output += "Content-Type: x/x\r\n"
+    output += request.GET.first("nosniff") + "\r\n"
+    output += "\r\n"
+    output += "// nothing to see here"
+    response.writer.write(output)
+    response.close_connection = True
diff --git a/fetch/nosniff/resources/x-content-type-options.json b/fetch/nosniff/resources/x-content-type-options.json
new file mode 100644
index 00000000000000..0a8c490756e674
--- /dev/null
+++ b/fetch/nosniff/resources/x-content-type-options.json
@@ -0,0 +1,58 @@
+[
+  {
+    "input": "X-Content-Type-Options: NOSNIFF",
+    "nosniff": true
+  },
+  {
+    "input": "x-content-type-OPTIONS: nosniff",
+    "nosniff": true
+  },
+  {
+    "input": "X-Content-Type-Options: nosniff,,@#$#%%&^&^*()()11!",
+    "nosniff": true
+  },
+  {
+    "input": "X-Content-Type-Options: @#$#%%&^&^*()()11!,nosniff",
+    "nosniff": false
+  },
+  {
+    "input": "X-Content-Type-Options: nosniff\r\nX-Content-Type-Options: no",
+    "nosniff": true
+  },
+  {
+    "input": "X-Content-Type-Options: no\r\nX-Content-Type-Options: nosniff",
+    "nosniff": false
+  },
+  {
+    "input": "X-Content-Type-Options:\r\nX-Content-Type-Options: nosniff",
+    "nosniff": false
+  },
+  {
+    "input": "X-Content-Type-Options: ,nosniff",
+    "nosniff": false
+  },
+  {
+    "input": "X-Content-Type-Options: nosniff\u000C",
+    "nosniff": false
+  },
+  {
+    "input": "X-Content-Type-Options: nosniff\u000B",
+    "nosniff": false
+  },
+  {
+    "input": "X-Content-Type-Options: nosniff\u000B,nosniff",
+    "nosniff": false
+  },
+  {
+    "input": "X-Content-Type-Options: 'NosniFF'",
+    "nosniff": false
+  },
+  {
+    "input": "X-Content-Type-Options: \"nosniFF\"",
+    "nosniff": false
+  },
+  {
+    "input": "Content-Type-Options: nosniff",
+    "nosniff": false
+  }
+]