diff --git a/Libraries/LibWeb/DOM/Element.cpp b/Libraries/LibWeb/DOM/Element.cpp
index 79d02af5820b1..3cc81c50748e1 100644
--- a/Libraries/LibWeb/DOM/Element.cpp
+++ b/Libraries/LibWeb/DOM/Element.cpp
@@ -463,16 +463,16 @@ WebIDL::ExceptionOr<QualifiedName> validate_and_extract(JS::Realm& realm, Option
     auto local_name = qualified_name;
 
     // 4. If qualifiedName contains a U+003A (:):
-    auto split_result = qualified_name.bytes_as_string_view().split_view(':', SplitBehavior::KeepEmpty);
-    if (split_result.size() > 1) {
-        // 1. Let splitResult be the result of running strictly split given qualifiedName and U+003A (:).
-        // 2. Set prefix to splitResult[0].
-        prefix = MUST(FlyString::from_utf8(split_result[0]));
+    auto qualified_name_view = qualified_name.bytes_as_string_view();
+    auto colon_position = qualified_name_view.find(':');
+    if (colon_position.has_value()) {
+        // 1. Set prefix to the part of qualifiedName before the first U+003A (:).
+        prefix = MUST(FlyString::from_utf8(qualified_name_view.substring_view(0, *colon_position)));
 
-        // 3. Set localName to splitResult[1].
-        local_name = MUST(FlyString::from_utf8(split_result[1]));
+        // 2. Set localName to the part of qualifiedName after the first U+003A (:).
+        local_name = MUST(FlyString::from_utf8(qualified_name_view.substring_view(*colon_position + 1)));
 
-        // 4. If prefix is not a valid namespace prefix, then throw an "InvalidCharacterError" DOMException.
+        // 3. If prefix is not a valid namespace prefix, then throw an "InvalidCharacterError" DOMException.
         if (!is_valid_namespace_prefix(*prefix))
             return WebIDL::InvalidCharacterError::create(realm, "Prefix not a valid namespace prefix."_utf16);
     }
diff --git a/Tests/LibWeb/Text/expected/wpt-import/dom/nodes/DOMImplementation-createDocument.txt b/Tests/LibWeb/Text/expected/wpt-import/dom/nodes/DOMImplementation-createDocument.txt
index 545058716898e..fe54ed676c5eb 100644
--- a/Tests/LibWeb/Text/expected/wpt-import/dom/nodes/DOMImplementation-createDocument.txt
+++ b/Tests/LibWeb/Text/expected/wpt-import/dom/nodes/DOMImplementation-createDocument.txt
@@ -1,8 +1,8 @@
 Harness status: OK
 
-Found 430 tests
+Found 434 tests
 
-430 Pass
+434 Pass
 Pass	DOMImplementation.createDocument(namespace, qualifiedName, doctype)
 Pass	createDocument test: null,null,null,null
 Pass	createDocument test: metadata for null,null,null
@@ -93,7 +93,7 @@ Pass	createDocument test: characterSet aliases for undefined,"foo1",null
 Pass	createDocument test: undefined,":foo",null,"INVALID_CHARACTER_ERR"
 Pass	createDocument test: undefined,"f:oo",null,"NAMESPACE_ERR"
 Pass	createDocument test: undefined,"foo:",null,"INVALID_CHARACTER_ERR"
-Pass	createDocument test: undefined,"f::oo",null,"INVALID_CHARACTER_ERR"
+Pass	createDocument test: undefined,"f::oo",null,"NAMESPACE_ERR"
 Pass	createDocument test: undefined,"xml",null,null
 Pass	createDocument test: metadata for undefined,"xml",null
 Pass	createDocument test: characterSet aliases for undefined,"xml",null
@@ -128,7 +128,9 @@ Pass	createDocument test: "http://example.com/","f:o:o",null,null
 Pass	createDocument test: metadata for "http://example.com/","f:o:o",null
 Pass	createDocument test: characterSet aliases for "http://example.com/","f:o:o",null
 Pass	createDocument test: "http://example.com/","foo:",null,"INVALID_CHARACTER_ERR"
-Pass	createDocument test: "http://example.com/","f::oo",null,"INVALID_CHARACTER_ERR"
+Pass	createDocument test: "http://example.com/","f::oo",null,null
+Pass	createDocument test: metadata for "http://example.com/","f::oo",null
+Pass	createDocument test: characterSet aliases for "http://example.com/","f::oo",null
 Pass	createDocument test: "http://example.com/","a:0",null,"INVALID_CHARACTER_ERR"
 Pass	createDocument test: "http://example.com/","0:a",null,null
 Pass	createDocument test: metadata for "http://example.com/","0:a",null
@@ -213,7 +215,9 @@ Pass	createDocument test: characterSet aliases for "http://example.com/","XMLNS:
 Pass	createDocument test: "http://example.com/","xmlfoo:bar",null,null
 Pass	createDocument test: metadata for "http://example.com/","xmlfoo:bar",null
 Pass	createDocument test: characterSet aliases for "http://example.com/","xmlfoo:bar",null
-Pass	createDocument test: "http://example.com/","prefix::local",null,"INVALID_CHARACTER_ERR"
+Pass	createDocument test: "http://example.com/","prefix::local",null,null
+Pass	createDocument test: metadata for "http://example.com/","prefix::local",null
+Pass	createDocument test: characterSet aliases for "http://example.com/","prefix::local",null
 Pass	createDocument test: "http://example.com/","namespaceURI:{",null,"INVALID_CHARACTER_ERR"
 Pass	createDocument test: "http://example.com/","namespaceURI:}",null,"INVALID_CHARACTER_ERR"
 Pass	createDocument test: "http://example.com/","namespaceURI:~",null,"INVALID_CHARACTER_ERR"
diff --git a/Tests/LibWeb/Text/expected/wpt-import/dom/nodes/Document-createElementNS.txt b/Tests/LibWeb/Text/expected/wpt-import/dom/nodes/Document-createElementNS.txt
index e30db6cb8b537..c7d0bcddf42c6 100644
--- a/Tests/LibWeb/Text/expected/wpt-import/dom/nodes/Document-createElementNS.txt
+++ b/Tests/LibWeb/Text/expected/wpt-import/dom/nodes/Document-createElementNS.txt
@@ -144,9 +144,9 @@ Pass	createElementNS test in XHTML document: undefined,"f:oo","NAMESPACE_ERR"
 Pass	createElementNS test in HTML document: undefined,"foo:","INVALID_CHARACTER_ERR"
 Pass	createElementNS test in XML document: undefined,"foo:","INVALID_CHARACTER_ERR"
 Pass	createElementNS test in XHTML document: undefined,"foo:","INVALID_CHARACTER_ERR"
-Pass	createElementNS test in HTML document: undefined,"f::oo","INVALID_CHARACTER_ERR"
-Pass	createElementNS test in XML document: undefined,"f::oo","INVALID_CHARACTER_ERR"
-Pass	createElementNS test in XHTML document: undefined,"f::oo","INVALID_CHARACTER_ERR"
+Pass	createElementNS test in HTML document: undefined,"f::oo","NAMESPACE_ERR"
+Pass	createElementNS test in XML document: undefined,"f::oo","NAMESPACE_ERR"
+Pass	createElementNS test in XHTML document: undefined,"f::oo","NAMESPACE_ERR"
 Pass	createElementNS test in HTML document: undefined,"xml",null
 Pass	createElementNS test in XML document: undefined,"xml",null
 Pass	createElementNS test in XHTML document: undefined,"xml",null
@@ -201,9 +201,9 @@ Pass	createElementNS test in XHTML document: "http://example.com/","f:o:o",null
 Pass	createElementNS test in HTML document: "http://example.com/","foo:","INVALID_CHARACTER_ERR"
 Pass	createElementNS test in XML document: "http://example.com/","foo:","INVALID_CHARACTER_ERR"
 Pass	createElementNS test in XHTML document: "http://example.com/","foo:","INVALID_CHARACTER_ERR"
-Pass	createElementNS test in HTML document: "http://example.com/","f::oo","INVALID_CHARACTER_ERR"
-Pass	createElementNS test in XML document: "http://example.com/","f::oo","INVALID_CHARACTER_ERR"
-Pass	createElementNS test in XHTML document: "http://example.com/","f::oo","INVALID_CHARACTER_ERR"
+Pass	createElementNS test in HTML document: "http://example.com/","f::oo",null
+Pass	createElementNS test in XML document: "http://example.com/","f::oo",null
+Pass	createElementNS test in XHTML document: "http://example.com/","f::oo",null
 Pass	createElementNS test in HTML document: "http://example.com/","a:0","INVALID_CHARACTER_ERR"
 Pass	createElementNS test in XML document: "http://example.com/","a:0","INVALID_CHARACTER_ERR"
 Pass	createElementNS test in XHTML document: "http://example.com/","a:0","INVALID_CHARACTER_ERR"
@@ -300,9 +300,9 @@ Pass	createElementNS test in XHTML document: "http://example.com/","XMLNS:foo",n
 Pass	createElementNS test in HTML document: "http://example.com/","xmlfoo:bar",null
 Pass	createElementNS test in XML document: "http://example.com/","xmlfoo:bar",null
 Pass	createElementNS test in XHTML document: "http://example.com/","xmlfoo:bar",null
-Pass	createElementNS test in HTML document: "http://example.com/","prefix::local","INVALID_CHARACTER_ERR"
-Pass	createElementNS test in XML document: "http://example.com/","prefix::local","INVALID_CHARACTER_ERR"
-Pass	createElementNS test in XHTML document: "http://example.com/","prefix::local","INVALID_CHARACTER_ERR"
+Pass	createElementNS test in HTML document: "http://example.com/","prefix::local",null
+Pass	createElementNS test in XML document: "http://example.com/","prefix::local",null
+Pass	createElementNS test in XHTML document: "http://example.com/","prefix::local",null
 Pass	createElementNS test in HTML document: "http://example.com/","namespaceURI:{","INVALID_CHARACTER_ERR"
 Pass	createElementNS test in XML document: "http://example.com/","namespaceURI:{","INVALID_CHARACTER_ERR"
 Pass	createElementNS test in XHTML document: "http://example.com/","namespaceURI:{","INVALID_CHARACTER_ERR"
diff --git a/Tests/LibWeb/Text/input/wpt-import/dom/nodes/DOMImplementation-createDocument.html b/Tests/LibWeb/Text/input/wpt-import/dom/nodes/DOMImplementation-createDocument.html
index 3b3a26a641683..260882c3f04a8 100644
--- a/Tests/LibWeb/Text/input/wpt-import/dom/nodes/DOMImplementation-createDocument.html
+++ b/Tests/LibWeb/Text/input/wpt-import/dom/nodes/DOMImplementation-createDocument.html
@@ -116,7 +116,7 @@
           var names = []
           var firstColonIndex = qualified.indexOf(":")
           if (firstColonIndex >= 0) {
-            names = qualifiedName.split(":", 2);
+            names = [qualified.substring(0, firstColonIndex), qualified.substring(firstColonIndex + 1)];
           } else {
             names = [null, qualified]
           }
diff --git a/Tests/LibWeb/Text/input/wpt-import/dom/nodes/Document-createElementNS.html b/Tests/LibWeb/Text/input/wpt-import/dom/nodes/Document-createElementNS.html
index 8dc7ca4b4f672..66f612baab239 100644
--- a/Tests/LibWeb/Text/input/wpt-import/dom/nodes/Document-createElementNS.html
+++ b/Tests/LibWeb/Text/input/wpt-import/dom/nodes/Document-createElementNS.html
@@ -59,19 +59,17 @@
           assert_equals(element.nodeValue, null)
           assert_equals(element.ownerDocument, doc)
           var qualified = String(qualifiedName)
-          var tagName = String(qualifiedName)
           var names = [];
           var firstColonIndex = qualified.indexOf(":")
           if (firstColonIndex >= 0) {
-            names = qualifiedName.split(":", 2);
-            tagName = names.join(":");
+            names = [qualified.substring(0, firstColonIndex), qualified.substring(firstColonIndex + 1)];
           } else {
             names = [null, qualified]
           }
           assert_equals(element.prefix, names[0], 'element.prefix')
           assert_equals(element.localName, names[1], 'element.localName')
-          assert_equals(element.tagName, tagName, 'element.tagName')
-          assert_equals(element.nodeName, tagName, 'element.nodeName')
+          assert_equals(element.tagName, qualified, 'element.tagName')
+          assert_equals(element.nodeName, qualified, 'element.nodeName')
           assert_equals(element.namespaceURI,
                         namespace === undefined || namespace === "" ? null
                                                                     : namespace,
diff --git a/Tests/LibWeb/Text/input/wpt-import/dom/nodes/Document-createElementNS.js b/Tests/LibWeb/Text/input/wpt-import/dom/nodes/Document-createElementNS.js
index 21902ec504e76..14b22220ad91c 100644
--- a/Tests/LibWeb/Text/input/wpt-import/dom/nodes/Document-createElementNS.js
+++ b/Tests/LibWeb/Text/input/wpt-import/dom/nodes/Document-createElementNS.js
@@ -51,7 +51,7 @@ var createElementNS_tests = [
   [undefined, ":foo", "INVALID_CHARACTER_ERR"],
   [undefined, "f:oo", "NAMESPACE_ERR"],
   [undefined, "foo:", "INVALID_CHARACTER_ERR"],
-  [undefined, "f::oo", "INVALID_CHARACTER_ERR"],
+  [undefined, "f::oo", "NAMESPACE_ERR"],
   [undefined, "xml", null],
   [undefined, "xmlns", "NAMESPACE_ERR"],
   [undefined, "xmlfoo", null],
@@ -70,7 +70,7 @@ var createElementNS_tests = [
   ["http://example.com/", "f:oo", null],
   ["http://example.com/", "f:o:o", null],
   ["http://example.com/", "foo:", "INVALID_CHARACTER_ERR"],
-  ["http://example.com/", "f::oo", "INVALID_CHARACTER_ERR"],
+  ["http://example.com/", "f::oo", null],
   ["http://example.com/", "a:0", "INVALID_CHARACTER_ERR"],
   ["http://example.com/", "0:a", null],
   ["http://example.com/", "a:_", null],
@@ -103,7 +103,7 @@ var createElementNS_tests = [
   ["http://example.com/", "xmlns:foo", "NAMESPACE_ERR"],
   ["http://example.com/", "XMLNS:foo", null],
   ["http://example.com/", "xmlfoo:bar", null],
-  ["http://example.com/", "prefix::local", "INVALID_CHARACTER_ERR"],
+  ["http://example.com/", "prefix::local", null],
   ["http://example.com/", "namespaceURI:{", "INVALID_CHARACTER_ERR"],
   ["http://example.com/", "namespaceURI:}", "INVALID_CHARACTER_ERR"],
   ["http://example.com/", "namespaceURI:~", "INVALID_CHARACTER_ERR"],