diff --git a/assets/l10n/app_en.arb b/assets/l10n/app_en.arb
index e8366bf1098..5ec9b94b09d 100644
--- a/assets/l10n/app_en.arb
+++ b/assets/l10n/app_en.arb
@@ -67,6 +67,10 @@
   "@errorQuotationFailed": {
     "description": "Error message when quoting a message failed."
   },
+  "successLinkCopied": "Link copied",
+  "@successLinkCopied": {
+    "description": "Success message after copy link action completed."
+  },
   "successMessageCopied": "Message Copied",
   "@successMessageCopied": {
     "description": "Message when content of a message was copied to the users system clipboard."
@@ -83,6 +87,10 @@
   "@errorDialogContinue": {
     "description": "Button label in error dialogs to acknowledge error."
   },
+  "lightboxCopyLinkTooltip": "Copy link",
+  "@lightboxCopyLinkTooltip": {
+    "description": "Tooltip in lightbox for the copy link action."
+  },
   "subscribedToNStreams": "Subscribed to {num, plural, =0{no streams} =1{1 stream} other{{num} streams}}",
   "@subscribedToNStreams": {
     "description": "Test page label showing number of streams user is subscribed to.",
diff --git a/lib/widgets/lightbox.dart b/lib/widgets/lightbox.dart
index 829b7ab5270..4f47e9e9195 100644
--- a/lib/widgets/lightbox.dart
+++ b/lib/widgets/lightbox.dart
@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
+import 'package:flutter_gen/gen_l10n/zulip_localizations.dart';
 import 'package:intl/intl.dart';
 
 import '../api/model/model.dart';
@@ -70,12 +71,13 @@ class _CopyLinkButton extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final zulipLocalizations = ZulipLocalizations.of(context);
     return IconButton(
-      tooltip: 'Copy link',
+      tooltip: zulipLocalizations.lightboxCopyLinkTooltip,
       icon: const Icon(Icons.copy),
       onPressed: () async {
-        // TODO(i18n)
-        copyWithPopup(context: context, successContent: const Text('Link copied'),
+        copyWithPopup(context: context,
+          successContent: Text(zulipLocalizations.successLinkCopied),
           data: ClipboardData(text: url.toString()));
       });
   }
@@ -136,7 +138,7 @@ class _LightboxPageState extends State<_LightboxPage> {
     if (_headerFooterVisible) {
       // TODO(#45): Format with e.g. "Yesterday at 4:47 PM"
       final timestampText = DateFormat
-        .yMMMd(/* TODO(i18n): Pass selected language here, I think? */)
+        .yMMMd(/* TODO(#278): Pass selected language here, I think? */)
         .add_Hms()
         .format(DateTime.fromMillisecondsSinceEpoch(widget.message.timestamp * 1000));