diff --git a/python/l10n/fluent_migrations/bug_1731353_commonDialog.py b/python/l10n/fluent_migrations/bug_1731353_commonDialog.py
new file mode 100644
index 000000000000..74e9f17e89da
--- /dev/null
+++ b/python/l10n/fluent_migrations/bug_1731353_commonDialog.py
@@ -0,0 +1,30 @@
+# coding=utf8
+
+# Any copyright is dedicated to the Public Domain.
+# http://creativecommons.org/publicdomain/zero/1.0/
+
+from __future__ import absolute_import
+import fluent.syntax.ast as FTL
+from fluent.migrate.helpers import transforms_from
+from fluent.migrate.helpers import COPY
+
+
+def migrate(ctx):
+    """Bug 1731353 - Migrate commonDialog strings from DTD to FTL, part {index}"""
+
+    ctx.add_transforms(
+        "toolkit/toolkit/global/commonDialog.ftl",
+        "toolkit/toolkit/global/commonDialog.ftl",
+        transforms_from(
+            """
+
+common-dialog-copy-cmd =
+    .label = { COPY(path1, "copyCmd.label") }
+    .accesskey = { COPY(path1, "copyCmd.accesskey") }
+common-dialog-select-all-cmd =
+    .label = { COPY(path1, "selectAllCmd.label") }
+    .accesskey = { COPY(path1, "selectAllCmd.accesskey") }
+""",
+            path1="toolkit/chrome/global/commonDialog.dtd",
+        ),
+    )
diff --git a/toolkit/components/prompts/content/commonDialog.xhtml b/toolkit/components/prompts/content/commonDialog.xhtml
index ca35edf67b9b..f9e378adda38 100644
--- a/toolkit/components/prompts/content/commonDialog.xhtml
+++ b/toolkit/components/prompts/content/commonDialog.xhtml
@@ -8,7 +8,7 @@
 <?xml-stylesheet href="chrome://global/content/commonDialog.css" type="text/css"?>
 <?xml-stylesheet href="chrome://global/skin/commonDialog.css" type="text/css"?>
 
-<!DOCTYPE window SYSTEM "chrome://global/locale/commonDialog.dtd">
+<!DOCTYPE window>
 
 <window id="commonDialogWindow"
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
@@ -45,13 +45,11 @@
     <menupopup id="contentAreaContextMenu"
                onpopupshowing="goUpdateCommand('cmd_copy')">
       <menuitem id="context-copy"
-                label="&copyCmd.label;"
-                accesskey="&copyCmd.accesskey;"
+                data-l10n-id="common-dialog-copy-cmd"
                 command="cmd_copy"
                 disabled="true"/>
       <menuitem id="context-selectall"
-                label="&selectAllCmd.label;"
-                accesskey="&selectAllCmd.accesskey;"
+                data-l10n-id="common-dialog-select-all-cmd"
                 command="cmd_selectAll"/>
     </menupopup>
   </popupset>
diff --git a/toolkit/components/prompts/content/selectDialog.xhtml b/toolkit/components/prompts/content/selectDialog.xhtml
index 3d1f0e740091..877e0e71403a 100644
--- a/toolkit/components/prompts/content/selectDialog.xhtml
+++ b/toolkit/components/prompts/content/selectDialog.xhtml
@@ -5,7 +5,7 @@
    - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
 
 <?xml-stylesheet href="chrome://global/skin/global.css" type="text/css"?>
-<!DOCTYPE window SYSTEM "chrome://global/locale/commonDialog.dtd">
+<!DOCTYPE window>
 
 <window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
 <dialog>
diff --git a/toolkit/locales/en-US/chrome/global/commonDialog.dtd b/toolkit/locales/en-US/chrome/global/commonDialog.dtd
index c5ceea07bfc3..daa6ac034180 100644
--- a/toolkit/locales/en-US/chrome/global/commonDialog.dtd
+++ b/toolkit/locales/en-US/chrome/global/commonDialog.dtd
@@ -4,7 +4,3 @@
 
 <!ENTITY editfield0.label "User Name:">
 <!ENTITY editfield1.label "Password:">
-<!ENTITY copyCmd.label    "Copy">
-<!ENTITY copyCmd.accesskey "C">
-<!ENTITY selectAllCmd.label "Select All">
-<!ENTITY selectAllCmd.accesskey "A">
diff --git a/toolkit/locales/en-US/toolkit/global/commonDialog.ftl b/toolkit/locales/en-US/toolkit/global/commonDialog.ftl
index b76ec85a5a6d..1629a0d3330c 100644
--- a/toolkit/locales/en-US/toolkit/global/commonDialog.ftl
+++ b/toolkit/locales/en-US/toolkit/global/commonDialog.ftl
@@ -11,3 +11,10 @@ common-dialog-username =
   .value = Username
 common-dialog-password =
   .value = Password
+
+common-dialog-copy-cmd =
+    .label = Copy
+    .accesskey = C
+common-dialog-select-all-cmd =
+    .label = Select All
+    .accesskey = A