diff --git a/src/hooks/useGitHubAuth.ts b/src/hooks/useGitHubAuth.ts
index a0c24b2a..98267109 100644
--- a/src/hooks/useGitHubAuth.ts
+++ b/src/hooks/useGitHubAuth.ts
@@ -1,18 +1,73 @@
-import { useState, useMemo } from 'react';
+import { useState, useMemo, useEffect } from 'react';
 import { Octokit } from '@octokit/core';
 
 export const useGitHubAuth = () => {
   const [username, setUsername] = useState('');
   const [token, setToken] = useState('');
+  const [error, setError] = useState('');
 
   const octokit = useMemo(() => {
     if (!username) return null;
     if(token){
-    return new Octokit({ auth: token });
+      return new Octokit({ auth: token });
     }
     return new Octokit();
   }, [username, token]);
 
+  // Clear error when username or token changes, before validation runs
+  useEffect(() => {
+    setError('');
+  }, [username, token]);
+
+  // Validate token format and authentication on mount or change
+  useEffect(() => {
+    if (!token || !username) {
+      return;
+    }
+
+    const controller = new AbortController();
+
+    const validateAuth = async () => {
+      if (!octokit) return;
+      
+      try {
+        // Attempt a simple API call to verify the token is valid
+        await octokit.request('GET /user', { request: { signal: controller.signal } });
+        // Only update state if request was not aborted
+        if (!controller.signal.aborted) {
+          setError('');
+        }
+      } catch (err: unknown) {
+        // Ignore if request was aborted
+        if (controller.signal.aborted) {
+          return;
+        }
+
+        const error = err as {
+          status?: number;
+          message?: string;
+        };
+
+        if (error.status === 401) {
+          setError('Invalid personal access token. Please check and try again.');
+        } else if (error.status === 403) {
+          setError('Token has insufficient permissions or has expired.');
+        } else if (error.message?.includes('Bad credentials')) {
+          setError('Bad credentials. Please verify your personal access token.');
+        } else {
+          setError(`Authentication error: ${error.message || 'Unknown error'}`);
+        }
+      }
+    };
+
+    // Validate on token change (but with a small delay to avoid excessive API calls during typing)
+    const timeoutId = setTimeout(validateAuth, 500);
+    return () => {
+      clearTimeout(timeoutId);
+      controller.abort();
+    };
+  }, [token, username, octokit]);
+
   const getOctokit = () => octokit;
 
   return {
@@ -20,6 +75,8 @@ export const useGitHubAuth = () => {
     setUsername,
     token,
     setToken,
+    error,
+    setError,
     getOctokit,
   };
 };
diff --git a/src/pages/Tracker/Tracker.tsx b/src/pages/Tracker/Tracker.tsx
index 576f39bf..26c18f99 100644
--- a/src/pages/Tracker/Tracker.tsx
+++ b/src/pages/Tracker/Tracker.tsx
@@ -324,9 +324,15 @@ const Home: React.FC = () => {
         </FormControl>
       </Box>
 
-      {(authError || dataError) && (
+      {authError && (
         <Alert severity="error" sx={{ mb: 3 }}>
-          {authError || dataError}
+          <strong>Authentication Error:</strong> {authError}
+        </Alert>
+      )}
+
+      {dataError && !authError && (
+        <Alert severity="error" sx={{ mb: 3 }}>
+          <strong>Data Fetch Error:</strong> {dataError}
         </Alert>
       )}