diff --git a/src/app/community/page.tsx b/src/app/community/page.tsx
index db3b06d7..23788722 100644
--- a/src/app/community/page.tsx
+++ b/src/app/community/page.tsx
@@ -1,5 +1,6 @@
 'use client';
 
+import { AUTH_MESSAGES } from '@/lib/constants';
 import Fuse from 'fuse.js';
 import ReviewsSection from './ReviewsSection';
 import { useState, useEffect, useMemo } from 'react';
@@ -137,7 +138,7 @@ export default function CommunityPage() {
               <button
                 onClick={() => {
                   if (!user) {
-                    alert('Please login to start a discussion.');
+                    alert(AUTH_MESSAGES.LOGIN_TO_START_DISCUSSION);
                     return;
                   }
                   setShowCreateModal(true);
diff --git a/src/app/community/view/client.tsx b/src/app/community/view/client.tsx
index 3aa783f5..0e97bd9d 100644
--- a/src/app/community/view/client.tsx
+++ b/src/app/community/view/client.tsx
@@ -1,5 +1,6 @@
 'use client';
 
+import { AUTH_MESSAGES } from '@/lib/constants';
 import { useState, useEffect } from 'react';
 import { useAuth } from '@/context/AuthContext';
 import {
@@ -208,7 +209,7 @@ export default function DiscussionViewClient() {
 
   const handleReaction = async (emoji: string) => {
     if (!user || !discussionId) {
-      alert('Please login to react.');
+      alert(AUTH_MESSAGES.LOGIN_TO_REACT);
       return;
     }
 
@@ -479,7 +480,7 @@ export default function DiscussionViewClient() {
           ) : (
             <div className="text-center p-8 bg-muted/20 rounded-xl border border-border/50 border-dashed">
               <p className="text-muted-foreground">
-                Please login to reply to this discussion.
+                {AUTH_MESSAGES.LOGIN_TO_REPLY_TO_DISCUSSION}
               </p>
             </div>
           )}
diff --git a/src/app/opensource/page.tsx b/src/app/opensource/page.tsx
index d1c04b6e..de7c43fd 100644
--- a/src/app/opensource/page.tsx
+++ b/src/app/opensource/page.tsx
@@ -1,5 +1,6 @@
 'use client';
 
+import { AUTH_MESSAGES } from '@/lib/constants';
 import { useState, useEffect } from 'react';
 import {
   Github,
@@ -152,7 +153,7 @@ export default function OpenSourcePage() {
 
   const handleConnectGitHub = async () => {
     if (!user) {
-      alert('Please login to connect your GitHub account.');
+      alert(AUTH_MESSAGES.LOGIN_TO_CONNECT_GITHUB);
       return;
     }
 
diff --git a/src/app/u/client.tsx b/src/app/u/client.tsx
index 2c3d7e79..1309cb19 100644
--- a/src/app/u/client.tsx
+++ b/src/app/u/client.tsx
@@ -1,4 +1,5 @@
 'use client';
+import { AUTH_MESSAGES } from '@/lib/constants';
 const STATS_URL =
   process.env.NEXT_PUBLIC_GITHUB_STATS_URL ??
   'https://github-readme-stats-salesp07.vercel.app';
@@ -420,7 +421,7 @@ function ProfileContent({ uid }: { uid?: string }) {
     currentLikes: string[]
   ) => {
     if (!currentUser) {
-      alert('Please login to like projects.');
+      alert(AUTH_MESSAGES.LOGIN_TO_LIKE_PROJECTS);
       return;
     }
 
diff --git a/src/components/profile/FollowButton.tsx b/src/components/profile/FollowButton.tsx
index b8d24910..f5255e51 100644
--- a/src/components/profile/FollowButton.tsx
+++ b/src/components/profile/FollowButton.tsx
@@ -1,5 +1,6 @@
 'use client';
 
+import { AUTH_MESSAGES } from '@/lib/constants';
 import { useState, useEffect } from 'react';
 import { useAuth } from '@/context/AuthContext';
 import { UserPlus, UserCheck, Loader2 } from 'lucide-react';
@@ -31,7 +32,7 @@ export default function FollowButton({
 
   const handleFollowToggle = async () => {
     if (!user) {
-      alert('Please login to follow users.');
+      alert(AUTH_MESSAGES.LOGIN_TO_FOLLOW_USERS);
       return;
     }
     if (user.uid === targetUserId) return;
diff --git a/src/components/profile/UserProfile.tsx b/src/components/profile/UserProfile.tsx
index 4a3a9a47..1c75e523 100644
--- a/src/components/profile/UserProfile.tsx
+++ b/src/components/profile/UserProfile.tsx
@@ -1,4 +1,5 @@
 'use client';
+import { AUTH_MESSAGES } from '@/lib/constants';
 const AVATAR_FALLBACK =
   process.env.NEXT_PUBLIC_AVATAR_FALLBACK_URL ?? 'https://ui-avatars.com/api';
 import { useState, useEffect, useRef } from 'react';
@@ -407,7 +408,7 @@ export default function UserProfile() {
   if (!user) {
     return (
       <div className="flex items-center justify-center min-h-screen">
-        <p>Please login to view your profile.</p>
+        <p>{AUTH_MESSAGES.LOGIN_TO_VIEW_PROFILE}</p>
       </div>
     );
   }
diff --git a/src/components/projects/ProjectCard.tsx b/src/components/projects/ProjectCard.tsx
index e2c48be4..9636f44b 100644
--- a/src/components/projects/ProjectCard.tsx
+++ b/src/components/projects/ProjectCard.tsx
@@ -1,5 +1,6 @@
 'use client';
 
+import { AUTH_MESSAGES } from '@/lib/constants';
 import { useState, type ReactNode } from 'react';
 import { Target, ExternalLink, Edit3, Star, Bookmark } from 'lucide-react';
 import Image from 'next/image';
@@ -118,7 +119,7 @@ export default function ProjectCard({
   const handleToggleStar = async (e: React.MouseEvent) => {
     e.stopPropagation();
     if (!user) {
-      alert('Please login to star projects.');
+      alert(AUTH_MESSAGES.LOGIN_TO_STAR_PROJECTS);
       return;
     }
     if (isStarring) return;
diff --git a/src/components/resources/InternshipCalendarModal.tsx b/src/components/resources/InternshipCalendarModal.tsx
index ce428ff9..1a10fada 100644
--- a/src/components/resources/InternshipCalendarModal.tsx
+++ b/src/components/resources/InternshipCalendarModal.tsx
@@ -1,5 +1,6 @@
 'use client';
 
+import { AUTH_MESSAGES } from '@/lib/constants';
 import { useState, useEffect } from 'react';
 import { motion, AnimatePresence } from 'framer-motion';
 import {
@@ -84,7 +85,7 @@ export function InternshipCalendarModal({
 
   const handleStar = async () => {
     if (!user) {
-      alert('Please login to star resources!');
+      alert(AUTH_MESSAGES.LOGIN_TO_STAR_RESOURCES);
       return;
     }
 
diff --git a/src/lib/constants.ts b/src/lib/constants.ts
new file mode 100644
index 00000000..204a35b9
--- /dev/null
+++ b/src/lib/constants.ts
@@ -0,0 +1,24 @@
+/**
+ * Centralized static strings used across the app.
+ *
+ * Goal: avoid the same (or near-identical) hardcoded strings being
+ * duplicated across components, so copy changes only need to happen
+ * in one place.
+ *
+ * This file currently covers the "please log in to do X" family of
+ * messages, since those were the most widely duplicated pattern found
+ * across the codebase. Other scattered one-off alert/error strings can
+ * be migrated here incrementally in follow-up PRs.
+ */
+
+export const AUTH_MESSAGES = {
+  LOGIN_TO_STAR_PROJECTS: 'Please login to star projects.',
+  LOGIN_TO_STAR_RESOURCES: 'Please login to star resources!',
+  LOGIN_TO_REACT: 'Please login to react.',
+  LOGIN_TO_LIKE_PROJECTS: 'Please login to like projects.',
+  LOGIN_TO_FOLLOW_USERS: 'Please login to follow users.',
+  LOGIN_TO_CONNECT_GITHUB: 'Please login to connect your GitHub account.',
+  LOGIN_TO_START_DISCUSSION: 'Please login to start a discussion.',
+  LOGIN_TO_REPLY_TO_DISCUSSION: 'Please login to reply to this discussion.',
+  LOGIN_TO_VIEW_PROFILE: 'Please login to view your profile.',
+} as const;