diff --git a/ext/src/_locales/en/messages.json b/ext/src/_locales/en/messages.json
index da94803..57f45b9 100755
--- a/ext/src/_locales/en/messages.json
+++ b/ext/src/_locales/en/messages.json
@@ -1,229 +1,332 @@
 {
     "extensionName": {
         "message": "EXTENSION_NAME"
+      , "description": "Name of the extension and the native receiver selector window title."
     }
   , "extensionDescription": {
         "message": ""
+      , "description": "Description of the extension shown in the add-ons manager."
     }
 
+
   , "popupMediaTypeApp": {
         "message": "this site's app"
+      , "description": "Receiver selector media type <option> text for current site's sender application."
     }
   , "popupMediaTypeTab": {
         "message": "Tab"
+      , "description": "Receiver selector media type <option> text for current tab."
     }
   , "popupMediaTypeScreen": {
         "message": "Screen"
+      , "description": "Receiver selector media type <option> text for screen."
     }
+
   , "popupMediaSelectCastLabel": {
         "message": "Cast"
+      , "description": "(Cast) <select> to:"
     }
   , "popupMediaSelectToLabel": {
         "message": "to:"
+      , "description": "Cast <select> (to:)"
     }
   , "popupCastButtonTitle": {
         "message": "Cast"
+      , "description": "Button text for each receiver entry in the receiver selector."
     }
   , "popupCastingButtonTitle": {
-        "message": "Casting"
+        "message": "Casting$ellipsis$"
+      , "description": "Button text while establishing a session in the receiver selector. Ellipsis cycles (. → .. → ...) as loading indicator."
+      , "placeholders": {
+            "ellipsis": {
+                "content": "$1"
+              , "example": "..."
+            }
+        }
     }
 
+
   , "contextCast": {
         "message": "Cast..."
+      , "description": "Main context menu item title. Ellipsis indicates additional information required as it triggers opening of receiver selector."
     }
+
   , "contextAddToWhitelist": {
         "message": "Add to Whitelist"
+      , "description": "Top-level whitelist context menu item title."
     }
   , "contextAddToWhitelistRecommended": {
-        "message": "Add $1 (Recommended)"
+        "message": "Add $matchPattern$ (Recommended)"
+      , "description": "Context menu item title for recomended match pattern."
+      , "placeholders": {
+            "matchPattern": {
+                "content": "$1"
+              , "example": "https://example.com/*"
+            }
+        }
     }
   , "contextAddToWhitelistAdvancedAdd": {
-        "message": "Add $1"
+        "message": "Add $matchPattern$"
+      , "description": "Context menu item title for all other match patterns."
+      , "placeholders": {
+            "matchPattern": {
+                "content": "$1"
+              , "example": "*://*.example.com/*"
+            }
+        }
     }
 
 
   , "optionsBridgeLoading": {
         "message": "Loading bridge info..."
+      , "description": "Loading placeholder text for bridge section on options page."
     }
   , "optionsBridgeFoundStatusTitle": {
         "message": "Bridge found"
+      , "description": "Bridge OK status title text."
     }
   , "optionsBridgeIssueStatusTitle": {
         "message": "Bridge issue"
+      , "description": "Bridge error status title text."
     }
   , "optionsBridgeNotFoundStatusTitle": {
         "message": "Bridge not found"
+      , "description": "Bridge missing status title text."
     }
   , "optionsBridgeNotFoundStatusText": {
         "message": "Try downloading and installing the latest version."
+      , "description": "Bridge not found additional description text"
     }
-  , "optionsBridgeInfo": {
-        "message": "Bridge info:"
-    }
+
   , "optionsBridgeStatsName": {
         "message": "Name:"
+      , "description": "Bridge stats name row title."
     }
   , "optionsBridgeStatsVersion": {
         "message": "Version:"
+      , "description": "Bridge stats version row title."
     }
   , "optionsBridgeStatsExpectedVersion": {
         "message": "Expected version:"
+      , "description": "Bridge stats expected version row title."
     }
   , "optionsBridgeStatsCompatibility": {
         "message": "Compatibility:"
+      , "description": "Bridge stats compatibility row title."
     }
   , "optionsBridgeStatsRecommendedAction": {
         "message": "Recommended action:"
+      , "description": "Bridge stats recommended action row title."
     }
   , "optionsBridgeCompatible": {
         "message": "COMPATIBLE"
+      , "description": "Compatibility status is definitely compatible."
     }
   , "optionsBridgeLikelyCompatible": {
         "message": "LIKELY COMPATIBLE"
+      , "description": "Compatibility status is probably compatible."
     }
   , "optionsBridgeIncompatible": {
         "message": "INCOMPATIBLE"
+      , "description": "Compatibility status is definitely incompatible."
     }
   , "optionsBridgeOlderAction": {
         "message": "Bridge version older than expected, try updating bridge to the latest version."
+      , "description": "Recommended action for when the installed bridge version is older than the installed extension version."
     }
   , "optionsBridgeNewerAction": {
         "message": "Bridge version newer than expected, try updating extension to the latest version."
+      , "description": "Recommended action for when the installed bridge version is newer than the installed extension version."
     }
   , "optionsBridgeNoAction": {
         "message": "No action needed."
+      , "description": "Recommended action for when both bridge and extension versions are compatible or likely compatible."
     }
   , "optionsBridgeUpdateCheck": {
         "message": "Check for Updates"
+      , "description": "Update check button title."
     }
   , "optionsBridgeUpdateChecking": {
-        "message": "Checking for Updates$1"
+        "message": "Checking for Updates$ellipsis$"
+      , "description": "Update check button title while in progress. Ellipsis cycles (. → .. → ...) as loading indicator."
+      , "placeholders": {
+            "ellipsis": {
+                "content": "$1"
+              , "example": ".."
+            }
+        }
     }
   , "optionsBridgeUpdateStatusNoUpdates": {
         "message": "No updates available"
+      , "description": "Update status if no updates are found."
    }
   , "optionsBridgeUpdateStatusError": {
         "message": "Error checking for updates"
+      , "description": "Update status if an error was encountered checking for updates."
    }
   , "optionsBridgeUpdateAvailable": {
         "message": "An update is available:"
+      , "description": "Update status an update was found."
    }
   , "optionsBridgeUpdatePackageTypeSelect": {
         "message": "Select package type"
+      , "description": "Placeholder <select> value for Linux package type selection."
     }
   , "optionsBridgeUpdatePackageTypeDeb": {
         "message": ".deb (Debian/Ubuntu)"
+      , "description": "Linux .deb package type <option> text"
     }
   , "optionsBridgeUpdatePackageTypeRpm": {
         "message": ".rpm (Fedora)"
+      , "description": "Linux .rpm package type <option> text"
     }
   , "optionsBridgeUpdate": {
         "message": "Update Now..."
+      , "description": "Update now button title. Ellipsis indicates additional information as it triggers an update window popup."
     }
 
   , "optionsMediaCategoryName": {
         "message": "Media casting"
+      , "description": "Options page media casting category title."
     }
   , "optionsMediaCategoryDescription": {
         "message": "HTML5 video/audio media casting."
+      , "description": "Options page media casting category description."
     }
   , "optionsMediaEnabled": {
         "message": "Enable media casting"
+      , "description": "Media casting enabled checkbox label."
     }
   , "optionsMediaSyncElement": {
         "message": "Sync receiver state with media element"
+      , "description": "Media casting sync checkbox label."
     }
   , "optionsMediaStopOnUnload": {
         "message": "Stop receiver playback on page unload"
+      , "description": "Media stop on unload checkbox label."
     }
 
   , "optionsLocalMediaCategoryName": {
         "message": "Local media casting"
+      , "description": "Options page local media category title."
     }
   , "optionsLocalMediaCategoryDescription": {
         "message": "HTTP server started by the bridge app to stream local media files to the cast receiver."
+      , "description": "Options page local media category description."
     }
   , "optionsLocalMediaEnabled": {
         "message": "Enable local media casting"
+      , "description": "Local media enabled checkbox label."
     }
   , "optionsLocalMediaServerPort": {
         "message": "HTTP server port:"
+      , "description": "HTTP server port input label."
     }
 
   , "optionsUserAgentWhitelistCategoryName": {
         "message": "User agent whitelist"
+      , "description": "Options page whitelist category title."
     }
   , "optionsUserAgentWhitelistCategoryDescription": {
         "message": "Sites for which to replace the user agent with a Chrome version for compatibility. Must be valid match patterns."
+      , "description": "Options page whitelist category description."
     }
   , "optionsUserAgentWhitelistEnabled": {
         "message": "Enable site whitelist"
+      , "description": "Whitelist enabled checkbox label."
     }
   , "optionsUserAgentWhitelistContent": {
         "message": "Match patterns (newline-separated):"
+      , "description": "Match patterns editor widget label."
     }
   , "optionsUserAgentWhitelistBasicView": {
         "message": "Basic View"
+      , "description": "Switch to basic view button title."
     }
   , "optionsUserAgentWhitelistRawView": {
         "message": "Raw View"
+      , "description": "Switch to raw view button title."
     }
   , "optionsUserAgentWhitelistSaveRaw": {
         "message": "Save Raw"
+      , "description": "Save raw view edits button title."
     }
   , "optionsUserAgentWhitelistAddItem": {
         "message": "Add Item"
+      , "description": "Add new whitelist item button title."
     }
   , "optionsUserAgentWhitelistEditItem": {
         "message": "Edit"
+      , "description": "Edit whitelist item button title. Displayed on each item."
     }
   , "optionsUserAgentWhitelistRemoveItem": {
         "message": "Remove"
+      , "description": "Remove whitelist item button title. Displayed on each item."
     }
   , "optionsUserAgentWhitelistInvalidMatchPattern": {
-        "message": "Invalid match pattern $1"
+        "message": "Invalid match pattern $matchPattern$"
+      , "description": "Error displayed by input indicating an invalid match pattern."
+      , "placeholders": {
+            "matchPattern": {
+                "content": "$1"
+              , "example": "http://example"
+            }
+        }
     }
 
   , "optionsMirroringCategoryName": {
         "message": "Screen mirroring"
+      , "description": "Options page mirroring category name."
     }
   , "optionsMirroringCategoryDescription": {
         "message": "Screen/Tab mirroring to a Chromecast receiver app."
+      , "description": "Options page mirroring category description."
     }
   , "optionsMirroringEnabled": {
         "message": "Enable screen mirroring"
+      , "description": "Mirroring enabled checkbox label."
     }
   , "optionsMirroringAppId": {
         "message": "Receiver app ID:"
+      , "description": "Mirroring app ID input label."
     }
 
   , "optionsReset": {
         "message": "Restore Defaults"
+      , "description": "Restore default options button label."
     }
   , "optionsSave": {
         "message": "Save"
+      , "description": "Save options button label."
     }
   , "optionsSaved": {
         "message": "Saved!"
+      , "description": "Status text displayed by save button once options have been successfully saved."
     }
 
 
   , "updaterCancel": {
         "message": "Cancel"
+      , "description": "Updater cancel update download button title."
     }
   , "updaterDescriptionDownloading": {
         "message": "Downloading..."
+      , "description": "Updater status downloading title text."
     }
   , "updaterAdditionalDescriptionDownloading": {
         "message": "Fetching update package"
+      , "description": "Updater status downloading description text."
     }
   , "updaterDescriptionInstallReady": {
         "message": "Ready to install"
+      , "description": "Updater status ready to install title text."
     }
   , "updaterAdditionalDescriptionInstallReady": {
         "message": "The install package has been downloaded to your default downloads location."
+      , "description": "Updater status ready to install description text."
     }
   , "updaterInstall": {
         "message": "Install..."
+      , "description": "Updater install button title. Ellipsis indicates additional information as it triggers the some native UI for installing the package."
     }
 }
diff --git a/ext/src/_locales/nl/messages.json b/ext/src/_locales/nl/messages.json
index 3dd3f8e..5694fbb 100755
--- a/ext/src/_locales/nl/messages.json
+++ b/ext/src/_locales/nl/messages.json
@@ -33,9 +33,6 @@
   , "optionsBridgeNotFoundStatusText": {
         "message": "Probeer de nieuwste versie te installeren."
     }
-  , "optionsBridgeInfo": {
-        "message": "Bridge-informatie:"
-    }
   , "optionsBridgeStatsName": {
         "message": "Naam:"
     }
diff --git a/ext/src/ui/popup/index.tsx b/ext/src/ui/popup/index.tsx
index fd26f2e..24695a8 100755
--- a/ext/src/ui/popup/index.tsx
+++ b/ext/src/ui/popup/index.tsx
@@ -187,10 +187,10 @@ class ReceiverEntry extends Component<ReceiverEntryProps, ReceiverEntryState> {
                         onClick={ this.handleCast }
                         disabled={this.props.isLoading}>
                     { this.state.isLoading
-                        ? _("popupCastingButtonTitle") +
-                            (this.state.isLoading
-                                ? this.state.ellipsis
-                                : "")
+                        ? _("popupCastingButtonTitle"
+                              , (this.state.isLoading
+                                    ? this.state.ellipsis
+                                    : ""))
                         : _("popupCastButtonTitle") }
                 </button>
             </li>