diff --git a/editor/libeditor/EditorCommands.cpp b/editor/libeditor/EditorCommands.cpp
index beb4f060adc0..45f9e3198f72 100644
--- a/editor/libeditor/EditorCommands.cpp
+++ b/editor/libeditor/EditorCommands.cpp
@@ -269,7 +269,8 @@ bool UndoCommand::IsCommandEnabled(Command aCommand,
   if (!aEditorBase) {
     return false;
   }
-  return aEditorBase->IsSelectionEditable() && aEditorBase->CanUndo();
+  return aEditorBase->IsModifiable() && aEditorBase->IsSelectionEditable() &&
+         aEditorBase->CanUndo();
 }
 
 nsresult UndoCommand::DoCommand(Command aCommand, EditorBase& aEditorBase,
@@ -297,7 +298,8 @@ bool RedoCommand::IsCommandEnabled(Command aCommand,
   if (!aEditorBase) {
     return false;
   }
-  return aEditorBase->IsSelectionEditable() && aEditorBase->CanRedo();
+  return aEditorBase->IsModifiable() && aEditorBase->IsSelectionEditable() &&
+         aEditorBase->CanRedo();
 }
 
 nsresult RedoCommand::DoCommand(Command aCommand, EditorBase& aEditorBase,
@@ -548,7 +550,7 @@ bool SwitchTextDirectionCommand::IsCommandEnabled(
   if (!aEditorBase) {
     return false;
   }
-  return aEditorBase->IsSelectionEditable();
+  return aEditorBase->IsModifiable() && aEditorBase->IsSelectionEditable();
 }
 
 nsresult SwitchTextDirectionCommand::DoCommand(Command aCommand,
@@ -581,7 +583,8 @@ bool DeleteCommand::IsCommandEnabled(Command aCommand,
   // We can generally delete whenever the selection is editable.  However,
   // cmd_delete doesn't make sense if the selection is collapsed because it's
   // directionless.
-  bool isEnabled = aEditorBase->IsSelectionEditable();
+  bool isEnabled =
+      aEditorBase->IsModifiable() && aEditorBase->IsSelectionEditable();
 
   if (aCommand == Command::Delete && isEnabled) {
     return aEditorBase->CanDeleteSelection();
@@ -820,7 +823,7 @@ bool InsertPlaintextCommand::IsCommandEnabled(Command aCommand,
   if (!aEditorBase) {
     return false;
   }
-  return aEditorBase->IsSelectionEditable();
+  return aEditorBase->IsModifiable() && aEditorBase->IsSelectionEditable();
 }
 
 nsresult InsertPlaintextCommand::DoCommand(Command aCommand,
@@ -877,7 +880,7 @@ bool InsertParagraphCommand::IsCommandEnabled(Command aCommand,
   if (!aEditorBase || aEditorBase->IsSingleLineEditor()) {
     return false;
   }
-  return aEditorBase->IsSelectionEditable();
+  return aEditorBase->IsModifiable() && aEditorBase->IsSelectionEditable();
 }
 
 nsresult InsertParagraphCommand::DoCommand(Command aCommand,
@@ -918,7 +921,7 @@ bool InsertLineBreakCommand::IsCommandEnabled(Command aCommand,
   if (!aEditorBase || aEditorBase->IsSingleLineEditor()) {
     return false;
   }
-  return aEditorBase->IsSelectionEditable();
+  return aEditorBase->IsModifiable() && aEditorBase->IsSelectionEditable();
 }
 
 nsresult InsertLineBreakCommand::DoCommand(Command aCommand,
diff --git a/editor/libeditor/HTMLEditorCommands.cpp b/editor/libeditor/HTMLEditorCommands.cpp
index 1864299a3a4c..ecccc7c491cf 100644
--- a/editor/libeditor/HTMLEditorCommands.cpp
+++ b/editor/libeditor/HTMLEditorCommands.cpp
@@ -52,7 +52,7 @@ bool StateUpdatingCommandBase::IsCommandEnabled(Command aCommand,
   if (!htmlEditor) {
     return false;
   }
-  if (!htmlEditor->IsSelectionEditable()) {
+  if (!htmlEditor->IsModifiable() || !htmlEditor->IsSelectionEditable()) {
     return false;
   }
   if (aCommand == Command::FormatAbsolutePosition) {
@@ -355,8 +355,7 @@ bool RemoveListCommand::IsCommandEnabled(Command aCommand,
   if (!htmlEditor) {
     return false;
   }
-
-  if (!htmlEditor->IsSelectionEditable()) {
+  if (!htmlEditor->IsModifiable() || !htmlEditor->IsSelectionEditable()) {
     return false;
   }
 
@@ -401,7 +400,7 @@ bool IndentCommand::IsCommandEnabled(Command aCommand,
   if (!htmlEditor) {
     return false;
   }
-  return htmlEditor->IsSelectionEditable();
+  return htmlEditor->IsModifiable() && htmlEditor->IsSelectionEditable();
 }
 
 nsresult IndentCommand::DoCommand(Command aCommand, EditorBase& aEditorBase,
@@ -434,7 +433,7 @@ bool OutdentCommand::IsCommandEnabled(Command aCommand,
   if (!htmlEditor) {
     return false;
   }
-  return htmlEditor->IsSelectionEditable();
+  return htmlEditor->IsModifiable() && htmlEditor->IsSelectionEditable();
 }
 
 nsresult OutdentCommand::DoCommand(Command aCommand, EditorBase& aEditorBase,
@@ -467,7 +466,7 @@ bool MultiStateCommandBase::IsCommandEnabled(Command aCommand,
     return false;
   }
   // should be disabled sometimes, like if the current selection is an image
-  return htmlEditor->IsSelectionEditable();
+  return htmlEditor->IsModifiable() && htmlEditor->IsSelectionEditable();
 }
 
 nsresult MultiStateCommandBase::DoCommand(Command aCommand,
@@ -1047,7 +1046,7 @@ bool RemoveStylesCommand::IsCommandEnabled(Command aCommand,
     return false;
   }
   // test if we have any styles?
-  return htmlEditor->IsSelectionEditable();
+  return htmlEditor->IsModifiable() && htmlEditor->IsSelectionEditable();
 }
 
 nsresult RemoveStylesCommand::DoCommand(Command aCommand,
@@ -1085,7 +1084,7 @@ bool IncreaseFontSizeCommand::IsCommandEnabled(Command aCommand,
     return false;
   }
   // test if we are at max size?
-  return htmlEditor->IsSelectionEditable();
+  return htmlEditor->IsModifiable() && htmlEditor->IsSelectionEditable();
 }
 
 nsresult IncreaseFontSizeCommand::DoCommand(Command aCommand,
@@ -1121,7 +1120,7 @@ bool DecreaseFontSizeCommand::IsCommandEnabled(Command aCommand,
     return false;
   }
   // test if we are at min size?
-  return htmlEditor->IsSelectionEditable();
+  return htmlEditor->IsModifiable() && htmlEditor->IsSelectionEditable();
 }
 
 nsresult DecreaseFontSizeCommand::DoCommand(Command aCommand,
@@ -1156,7 +1155,7 @@ bool InsertHTMLCommand::IsCommandEnabled(Command aCommand,
   if (!htmlEditor) {
     return false;
   }
-  return htmlEditor->IsSelectionEditable();
+  return htmlEditor->IsModifiable() && htmlEditor->IsSelectionEditable();
 }
 
 nsresult InsertHTMLCommand::DoCommand(Command aCommand, EditorBase& aEditorBase,
@@ -1213,7 +1212,7 @@ bool InsertTagCommand::IsCommandEnabled(Command aCommand,
   if (!htmlEditor) {
     return false;
   }
-  return htmlEditor->IsSelectionEditable();
+  return htmlEditor->IsModifiable() && htmlEditor->IsSelectionEditable();
 }
 
 // corresponding STATE_ATTRIBUTE is: src (img) and href (a)
diff --git a/editor/libeditor/tests/mochitest.toml b/editor/libeditor/tests/mochitest.toml
index 7662d3fb719f..04f3e6a6b04e 100644
--- a/editor/libeditor/tests/mochitest.toml
+++ b/editor/libeditor/tests/mochitest.toml
@@ -418,6 +418,8 @@ skip-if = ["os == 'android'"] #Bug 1575739
 
 ["test_cmd_paragraphState.html"]
 
+["test_command_state_when_readonly.html"]
+
 ["test_composition_event_created_in_chrome.html"]
 
 ["test_composition_with_highlight_in_texteditor.html"]
diff --git a/editor/libeditor/tests/test_command_state_when_readonly.html b/editor/libeditor/tests/test_command_state_when_readonly.html
new file mode 100644
index 000000000000..7b4daaa1b37b
--- /dev/null
+++ b/editor/libeditor/tests/test_command_state_when_readonly.html
@@ -0,0 +1,149 @@
+<!doctype html>
+<title>Test for nsIEditor.isCommandEnabled for normal and read-only editors</title>
+<script src="/tests/SimpleTest/SimpleTest.js"></script>
+<script src="/tests/SimpleTest/EventUtils.js"></script>
+<link rel="stylesheet" href="/tests/SimpleTest/test.css">
+<div contenteditable></div>
+<script>
+  let node = document.querySelector("div");
+  node.focus();
+  let htmlEditor =
+    SpecialPowers.wrap(window).docShell.editingSession.getEditorForWindow(window);
+
+  // Supported environments for each command. Supported values for each
+  // environment property:
+  //   content: "empty", "non-empty", "cleared"
+  //   selected: true, false
+  //   readonly: true, false
+  //
+  // If an environment definition does not state a certain property, the command
+  // supports all possible values for that property. The following definition:
+  //    "cmd_copy": [{content: "non-empty", selected: true}],
+  // is equivalent to:
+  //    "cmd_copy": [
+  //      {content: "non-empty", selected: true, readonly: true},
+  //      {content: "non-empty", selected: true, readonly: false},
+  //    ],
+  const TEST_COMMANDS = {
+    "cmd_selectAll": [{content: "non-empty"}],
+
+    "cmd_copy": [{content: "non-empty", selected: true}],
+
+    "cmd_cut": [{content: "non-empty", selected: true, readonly: false}],
+    "cmd_delete": [{content: "non-empty", selected: true, readonly: false}],
+    "cmd_removeList":[{content: "non-empty", selected: true, readonly: false}],
+
+    "cmd_undo": [{content: "cleared", readonly: false}],
+    "cmd_redo": [{content: "cleared", readonly: false}],
+
+    "cmd_switchTextDirection": [{readonly: false}],
+    "cmd_bold": [{readonly: false}],
+    "cmd_italic": [{readonly: false}],
+    "cmd_underline": [{readonly: false}],
+    "cmd_em": [{readonly: false}],
+    "cmd_strong": [{readonly: false}],
+    "cmd_strikethrough": [{readonly: false}],
+    "cmd_superscript": [{readonly: false}],
+    "cmd_subscript": [{readonly: false}],
+    "cmd_indent": [{readonly: false}],
+    "cmd_outdent": [{readonly: false}],
+    "cmd_formatBlock": [{readonly: false}],
+    "cmd_paragraphState": [{readonly: false}],
+    "cmd_fontFace": [{readonly: false}],
+    "cmd_fontSize": [{readonly: false}],
+    "cmd_fontColor": [{readonly: false}],
+    "cmd_backgroundColor": [{readonly: false}],
+    "cmd_highlight": [{readonly: false}],
+    "cmd_align": [{readonly: false}],
+    "cmd_removeStyles": [{readonly: false}],
+    "cmd_increaseFont": [{readonly: false}],
+    "cmd_decreaseFont": [{readonly: false}],
+    "cmd_insertHR": [{readonly: false}],
+    "cmd_insertHTML": [{readonly: false}],
+    "cmd_insertText": [{readonly: false}],
+    "cmd_insertParagraph": [{readonly: false}],
+    "cmd_insertLineBreak": [{readonly: false}],
+    "cmd_tt":[{readonly: false}],
+    "cmd_nobreak":[{readonly: false}],
+    "cmd_cite":[{readonly: false}],
+    "cmd_abbr":[{readonly: false}],
+    "cmd_acronym":[{readonly: false}],
+    "cmd_code":[{readonly: false}],
+    "cmd_samp":[{readonly: false}],
+    "cmd_var":[{readonly: false}],
+    "cmd_removeLinks":[{readonly: false}],
+    "cmd_ol":[{readonly: false}],
+    "cmd_ul":[{readonly: false}],
+    "cmd_dt":[{readonly: false}],
+    "cmd_dd":[{readonly: false}],
+
+    // InsertTagCommand
+    "cmd_insertImageNoUI": [{readonly: false}],
+    "cmd_insertLinkNoUI": [{readonly: false}],
+  };
+
+  function testCommands(content) {
+    for (let readonly of [true, false]){
+      if (readonly) {
+        htmlEditor.flags |= SpecialPowers.Ci.nsIEditor.eEditorReadonlyMask;
+      } else {
+        htmlEditor.flags &= ~SpecialPowers.Ci.nsIEditor.eEditorReadonlyMask;
+      }
+
+      for (let selected of [true, false]) {
+        let selection = window.getSelection();
+        selection.collapse(node);
+
+        if (selected) {
+          if (content == "non-empty") {
+            // The command cmd_removeList needs selected text inside a list. It
+            // does not matter for all other commands, so lets just select that.
+            let range = document.createRange();
+            let li = document.querySelector("li");
+            range.selectNodeContents(li);
+            selection.removeAllRanges();
+            selection.addRange(range);
+          } else {
+            document.execCommand("selectAll");
+          }
+        }
+
+        for (let [cmd, supports] of Object.entries(TEST_COMMANDS)) {
+          // Check if the command should support this environment.
+          let expected = supports.some(supported =>
+            content == (supported?.content ?? content) &&
+            readonly == (supported?.readonly ?? readonly) &&
+            selected == (supported?.selected ?? selected)
+          )
+          is(
+            SpecialPowers.isCommandEnabled(window, cmd),
+            expected,
+            `Enabled state of command ${cmd} should be ${
+              expected ? "TRUE" : "FALSE"
+            } for ${JSON.stringify({content, selected, readonly})}`
+          );
+        }
+      }
+    }
+  }
+
+  testCommands("empty");
+
+  // The cmd_removeList command needs a list.
+  node.innerHTML = "<ul><li><span>abcd</span></li></ul>";
+  testCommands("non-empty");
+
+  // Make some content modifications to enable undo and redo.
+  node.innerText = "ABC";
+  is(node.innerText.trim(), "ABC", "phase 1");
+  document.execCommand("selectAll");
+  synthesizeKey("KEY_Backspace");
+  is(node.innerText.trim(), "", "phase 2");
+  synthesizeKey("3");
+  is(node.innerText.trim(), "3", "phase 3");
+  SpecialPowers.doCommand(window, "cmd_undo");
+  is(node.innerText.trim(), "", "phase 4");
+
+  node.innerHTML = "";
+  testCommands("cleared");
+</script>