diff --git a/Libraries/LibWeb/Editing/ExecCommand.cpp b/Libraries/LibWeb/Editing/ExecCommand.cpp
index b1c68f4e38a..e9c59b6fbdf 100644
--- a/Libraries/LibWeb/Editing/ExecCommand.cpp
+++ b/Libraries/LibWeb/Editing/ExecCommand.cpp
@@ -45,8 +45,11 @@ WebIDL::ExceptionOr<bool> Document::exec_command(FlyString const& command, [[may
     //    classified with the miscellaneous events, we'd have to stop firing events for consistency's sake.
     //
     // AD-HOC: The defaultParagraphSeparator command is also in the Miscellaneous commands section
+    auto optional_command = Editing::find_command_definition(command);
+    VERIFY(optional_command.has_value());
+    auto const& command_definition = optional_command.release_value();
     GC::Ptr<Node> affected_editing_host;
-    if (!command.is_one_of(Editing::CommandNames::copy, Editing::CommandNames::cut,
+    if (!command_definition.command.is_one_of(Editing::CommandNames::copy, Editing::CommandNames::cut,
             Editing::CommandNames::defaultParagraphSeparator, Editing::CommandNames::paste, Editing::CommandNames::redo,
             Editing::CommandNames::selectAll, Editing::CommandNames::styleWithCSS, Editing::CommandNames::undo,
             Editing::CommandNames::useCSS)) {
@@ -89,9 +92,6 @@ WebIDL::ExceptionOr<bool> Document::exec_command(FlyString const& command, [[may
 
     // https://w3c.github.io/editing/docs/execCommand/#preserves-overrides
     // If a command preserves overrides, then before taking its action, the user agent must record current overrides.
-    auto optional_command = Editing::find_command_definition(command);
-    VERIFY(optional_command.has_value());
-    auto const& command_definition = optional_command.release_value();
     Vector<Editing::RecordedOverride> overrides;
     if (command_definition.preserves_overrides)
         overrides = Editing::record_current_overrides(*this);
@@ -146,7 +146,7 @@ WebIDL::ExceptionOr<bool> Document::query_command_enabled(FlyString const& comma
     // Among commands defined in this specification, those listed in Miscellaneous commands are always enabled, except
     // for the cut command and the paste command.
     // NOTE: cut and paste are actually in the Clipboard commands section
-    if (command.is_one_of(
+    if (command.is_one_of_ignoring_ascii_case(
             Editing::CommandNames::defaultParagraphSeparator,
             Editing::CommandNames::redo,
             Editing::CommandNames::styleWithCSS,
@@ -155,7 +155,7 @@ WebIDL::ExceptionOr<bool> Document::query_command_enabled(FlyString const& comma
         return true;
 
     // AD-HOC: selectAll requires a selection object to exist.
-    if (command == Editing::CommandNames::selectAll)
+    if (command.equals_ignoring_ascii_case(Editing::CommandNames::selectAll))
         return get_selection() != nullptr;
 
     // The other commands defined here are enabled if the active range is not null,
@@ -195,7 +195,7 @@ WebIDL::ExceptionOr<bool> Document::query_command_enabled(FlyString const& comma
     //       the spec is that certain commands must not be enabled if the editing host is in the plaintext-only state.
     if (auto const* html_element = as_if<HTML::HTMLElement>(inclusive_ancestor_editing_host.ptr()); html_element
         && html_element->content_editable_state() == HTML::ContentEditableState::PlaintextOnly
-        && command.is_one_of(
+        && command.is_one_of_ignoring_ascii_case(
             Editing::CommandNames::backColor,
             Editing::CommandNames::bold,
             Editing::CommandNames::createLink,
@@ -242,7 +242,7 @@ WebIDL::ExceptionOr<bool> Document::query_command_indeterm(FlyString const& comm
         // https://w3c.github.io/editing/docs/execCommand/#inline-command-activated-values
         // If a command is a standard inline value command, it is indeterminate if among formattable nodes that are
         // effectively contained in the active range, there are two that have distinct effective command values.
-        if (command.is_one_of(Editing::CommandNames::backColor, Editing::CommandNames::fontName,
+        if (command_definition.command.is_one_of(Editing::CommandNames::backColor, Editing::CommandNames::fontName,
                 Editing::CommandNames::foreColor, Editing::CommandNames::hiliteColor)) {
             Optional<String> first_node_value;
             auto range = Editing::active_range(*this);
diff --git a/Tests/LibWeb/Text/expected/Editing/execCommand-case-insensitivity.txt b/Tests/LibWeb/Text/expected/Editing/execCommand-case-insensitivity.txt
new file mode 100644
index 00000000000..51d63d70e11
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/Editing/execCommand-case-insensitivity.txt
@@ -0,0 +1,9 @@
+queryCommandSupported("selectall"): true
+queryCommandEnabled("selectall"): true
+execCommand("selectall"): PASS
+queryCommandSupported("SELECTALL"): true
+queryCommandEnabled("SELECTALL"): true
+execCommand("SELECTALL"): PASS
+queryCommandSupported("SeLeCtAlL"): true
+queryCommandEnabled("SeLeCtAlL"): true
+execCommand("SeLeCtAlL"): PASS
diff --git a/Tests/LibWeb/Text/input/Editing/execCommand-case-insensitivity.html b/Tests/LibWeb/Text/input/Editing/execCommand-case-insensitivity.html
new file mode 100644
index 00000000000..01dd6ac05cb
--- /dev/null
+++ b/Tests/LibWeb/Text/input/Editing/execCommand-case-insensitivity.html
@@ -0,0 +1,29 @@
+<!DOCTYPE html>
+<script src="../include.js"></script>
+<body></body>
+<script>
+    function execCommandCaseInsensitivityTest(command) {
+        return new Promise((resolve) => {
+            const iframe = document.createElement("iframe");
+            iframe.srcdoc = `<div>PASS</div>`;
+            document.body.appendChild(iframe);
+            iframe.onload = () => {
+                const iframeDocument = iframe.contentDocument;
+                iframeDocument.execCommand(command);
+
+                const selection = iframeDocument.getSelection();
+                println(`queryCommandSupported("${command}"): ${iframeDocument.queryCommandSupported(command)}`);
+                println(`queryCommandEnabled("${command}"): ${iframeDocument.queryCommandEnabled(command)}`);
+                println(`execCommand("${command}"): ${selection.toString()}`);
+                iframe.remove();
+                resolve();
+            };
+        });
+    }
+    asyncTest(async done => {
+        for (command of ["selectall", "SELECTALL", "SeLeCtAlL"]) {
+            await execCommandCaseInsensitivityTest(command);
+        }
+        done();
+    });
+</script>