diff --git a/files/en-us/mozilla/add-ons/webextensions/api/tabs/duplicate/index.md b/files/en-us/mozilla/add-ons/webextensions/api/tabs/duplicate/index.md
index f4d7fe85798aec5..df8cba194821774 100644
--- a/files/en-us/mozilla/add-ons/webextensions/api/tabs/duplicate/index.md
+++ b/files/en-us/mozilla/add-ons/webextensions/api/tabs/duplicate/index.md
@@ -24,13 +24,13 @@ let duplicating = browser.tabs.duplicate(
 
 - `tabId`
   - : `integer`. The ID of the tab to be duplicated.
-- `duplicateProperties` Optional
+- `duplicateProperties` {{optional_inline}}
 
   - : `object`. An object describing how the tab is duplicated. It contains the following properties:
 
-    - `index` Optional
+    - `index` {{optional_inline}}
       - : `integer`. The position of the new tab in the window. The value is constrained to the range zero to the number of tabs in the window.
-    - `active` Optional
+    - `active` {{optional_inline}}
       - : `boolean`. Whether the tab becomes the active tab in the window. Does not affect whether the window is focused. Defaults to `true`.
 
 ### Return value