diff --git a/package-lock.json b/package-lock.json
index 2a30e3a..55b6683 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -15,7 +15,7 @@
         "@mui/icons-material": "^6.1.5",
         "@mui/material": "^6.1.5",
         "firebase": "^11.0.1",
-        "react": "^18.3.0",
+        "react": "^18.3.1",
         "react-dom": "^18.3.0",
         "react-router-dom": "^6.27.0"
       },
diff --git a/package.json b/package.json
index a0be452..3f8346c 100644
--- a/package.json
+++ b/package.json
@@ -28,7 +28,7 @@
     "@mui/icons-material": "^6.1.5",
     "@mui/material": "^6.1.5",
     "firebase": "^11.0.1",
-    "react": "^18.3.0",
+    "react": "^18.3.1",
     "react-dom": "^18.3.0",
     "react-router-dom": "^6.27.0"
   },
diff --git a/src/components/common/Header.jsx b/src/components/common/Header.jsx
new file mode 100644
index 0000000..84ef4c6
--- /dev/null
+++ b/src/components/common/Header.jsx
@@ -0,0 +1,63 @@
+import { AppBar, Avatar, Box, Button, IconButton, Toolbar, Typography } from '@mui/material';
+import { handleSignIn, handleSignOut } from '@utils/auth';
+import { auth } from '@utils/firebaseConfig';
+import { useEffect, useState } from 'react';
+import { useNavigate } from 'react-router-dom';
+
+const Header = () => {
+  const [user, setUser] = useState(null);
+  const navigate = useNavigate();
+
+  useEffect(() => {
+    const unsubscribe = auth.onAuthStateChanged((user) => {
+      setUser(user);
+    });
+    return () => unsubscribe();
+  }, []);
+
+  const handleAuthClick = async () => {
+    if (user) {
+      await handleSignOut(navigate);
+    } else {
+      await handleSignIn();
+    }
+  };
+
+  return (
+    <AppBar position="sticky" sx={{ backgroundColor: 'primary.light', color: '#000' }}>
+      <Toolbar sx={{ position: 'relative', justifyContent: 'space-between' }}>
+        <Box sx={{ display: 'flex', alignItems: 'center' }}>
+          {/* Placeholder Box for back button if needed in the future */}
+          <Box sx={{ width: '48px' }} />
+        </Box>
+
+        <Typography
+          variant="h6"
+          sx={{
+            position: 'absolute',
+            left: '50%',
+            transform: 'translateX(-50%)',
+            fontWeight: '600',
+            fontSize: '1.4rem',
+          }}
+        >
+          Stepwise
+        </Typography>
+
+        <Box sx={{ display: 'flex', alignItems: 'center' }}>
+          {user ? (
+            <IconButton edge="end" color="inherit" onClick={handleAuthClick}>
+              <Avatar alt={user.displayName} src={user.photoURL} />
+            </IconButton>
+          ) : (
+            <Button color="inherit" onClick={handleAuthClick}>
+              Sign In
+            </Button>
+          )}
+        </Box>
+      </Toolbar>
+    </AppBar>
+  );
+};
+
+export default Header;
diff --git a/src/pages/Home.jsx b/src/pages/Home.jsx
index 6270bf7..ced5c3b 100644
--- a/src/pages/Home.jsx
+++ b/src/pages/Home.jsx
@@ -1,5 +1,12 @@
+import Header from '@components/common/Header';
+
 const Home = () => {
-  return <h1>Home</h1>;
+  return (
+    <div>
+      <Header />
+      <h1>Home</h1>
+    </div>
+  );
 };
 
 export default Home;
diff --git a/src/utils/auth.js b/src/utils/auth.js
new file mode 100644
index 0000000..1cf069b
--- /dev/null
+++ b/src/utils/auth.js
@@ -0,0 +1,47 @@
+import { createFirstUserProfile, fetchUserProfile } from '@utils/firebase/createUserProfile';
+import { auth } from '@utils/firebaseConfig';
+import { GoogleAuthProvider, signInWithPopup, signOut } from 'firebase/auth';
+
+const provider = new GoogleAuthProvider();
+
+// Google Sign-In function
+const signInWithGoogle = async () => {
+  try {
+    const result = await signInWithPopup(auth, provider);
+    return result.user;
+  } catch (error) {
+    console.error('Error during sign-in:', error);
+    return null;
+  }
+};
+
+// Handle Sign-In
+// Returns true if the user already exists in the database, false if a new profile was created
+export const handleSignIn = async () => {
+  const user = await signInWithGoogle();
+
+  if (user) {
+    // Try to fetch the existing user profile
+    const { profile } = await fetchUserProfile(user.uid);
+
+    // If no profile found, create one with default data
+    if (!profile) {
+      await createFirstUserProfile(user);
+      return false; // New user profile created
+    }
+    return true; // User profile already exists
+  }
+  return false; // Sign-in failed or cancelled
+};
+
+// Handle Sign-Out
+// Redirects to homepage after sign-out
+export const handleSignOut = async (navigate) => {
+  try {
+    await signOut(auth);
+    console.log('Sign out successful');
+    navigate('/');
+  } catch (error) {
+    console.error('Error during sign-out:', error);
+  }
+};
diff --git a/src/utils/firebase/createUserProfile.js b/src/utils/firebase/createUserProfile.js
new file mode 100644
index 0000000..7656c7d
--- /dev/null
+++ b/src/utils/firebase/createUserProfile.js
@@ -0,0 +1,77 @@
+import { db } from '@utils/firebaseConfig';
+import { doc, getDoc, setDoc, updateDoc } from 'firebase/firestore';
+
+// Unified function to fetch and listen to user profile changes by UID
+// (supports both regular and transaction-based fetches)
+export const fetchUserProfile = async (uid, transaction = null) => {
+  try {
+    const userRef = doc(db, 'users', uid);
+
+    // If transaction is provided, use it to fetch the document
+    const userSnapshot = transaction ? await transaction.get(userRef) : await getDoc(userRef);
+
+    if (!userSnapshot.exists()) {
+      console.error(`User profile for ${uid} does not exist`);
+      return { ref: userRef, profile: null }; // Return consistent format with null profile
+    }
+
+    const profile = userSnapshot.data();
+    return { ref: userRef, profile };
+  } catch (error) {
+    console.error('Error fetching user profile:', error);
+    return { ref: null, profile: null };
+  }
+};
+
+// Check or create user profile in Firestore (uses fetchUserProfile to streamline code)
+export const createFirstUserProfile = async (user) => {
+  try {
+    const { uid, photoURL, displayName } = user;
+    const defaultProfile = {
+      uid,
+      profilePic: photoURL || '',
+      name: displayName || '',
+      goals: [
+        {
+          name: '',
+          progress: 0,
+          microgoals: [
+            {
+              name: '',
+              progress: 0,
+              tasks: [{ name: '', completed: false }],
+            },
+          ],
+        },
+      ],
+      streak: [],
+    };
+
+    // If the profile does not exist, create it with the default data
+    await setDoc(doc(db, 'users', uid), defaultProfile);
+    console.warn('New user profile created with default data.');
+
+    return true;
+  } catch (error) {
+    console.error('Error checking or creating user profile:', error);
+    return false; // Return false if an error occurs
+  }
+};
+
+// Get user profile by UID
+// (simple wrapper around fetchUserProfile for non-transaction use)
+export const getUserProfile = async (uid) => {
+  const fetchedUser = await fetchUserProfile(uid);
+  return fetchedUser ? fetchedUser.profile : null; // Return only the profile data
+};
+
+// Update user profile by UID
+export const updateUserProfile = async (uid, updates) => {
+  try {
+    const userDocRef = doc(db, 'users', uid);
+    await updateDoc(userDocRef, updates);
+    console.warn('User profile updated');
+  } catch (error) {
+    console.error('Error updating user profile:', error);
+  }
+};
diff --git a/src/utils/firebaseConfig.js b/src/utils/firebaseConfig.js
index 98f07d7..3ac43db 100644
--- a/src/utils/firebaseConfig.js
+++ b/src/utils/firebaseConfig.js
@@ -1,5 +1,12 @@
 // Import the functions you need from the SDKs you need
 import { initializeApp } from 'firebase/app';
+import { getAuth } from 'firebase/auth';
+import {
+  CACHE_SIZE_UNLIMITED,
+  initializeFirestore,
+  persistentLocalCache,
+  persistentSingleTabManager,
+} from 'firebase/firestore';
 // TODO: Add SDKs for Firebase products that you want to use
 // https://firebase.google.com/docs/web/setup#available-libraries
 
@@ -17,6 +24,13 @@ const firebaseConfig = {
 
 // Initialize Firebase
 const app = initializeApp(firebaseConfig);
-const db = getFirestore(app);
 
-export { db };
+// Enable IndexedDB persistence with single-tab manager
+export const db = initializeFirestore(app, {
+  localCache: persistentLocalCache({
+    tabManager: persistentSingleTabManager(),
+    cacheSizeBytes: CACHE_SIZE_UNLIMITED,
+  }),
+});
+
+export const auth = getAuth(app);