Step-by-Step Fix
-
Confirm the scope
- Try a different browser/device and a different network.
- If only one environment fails, the cause is usually local.
-
Refresh your session
- Sign out completely, then sign back in.
- Clear cache/cookies for the service domain.
- Try an incognito/private window with no extensions.
-
Check permissions and plan status
- Verify you’re using the correct account/workspace.
- Confirm your subscription/plan is active and assigned correctly.
-
Rule out network filtering
- Disable VPN/proxy temporarily.
- Pause ad blockers / privacy tools that may block requests.
- If you’re on a corporate network, test via hotspot.
-
Check service incidents
- Review the product status page or recent incident reports.
- If the service is degraded, wait and retry.
-
Collect evidence and escalate
- Save screenshots + exact error text + timestamps.
- Include environment details and repro steps in a support ticket.
Common Root Causes
- Expired/invalid session tokens
- Plan or permission mismatch
- Browser extensions interfering with requests
- Network blocks (VPN/proxy/firewall/DNS)
- Temporary outages
Prevention Tips
- Keep a clean browser profile for critical workflows
- Don’t stack multiple privacy extensions that rewrite requests
- Document workspace/team permissions and billing owners
- Export important settings regularly (when supported)
Why This Happens
Claude’s login flow uses OAuth-based authentication through Google, Apple, or email magic links. A verification loop occurs when the redirect between Anthropic’s auth server and your browser is interrupted—usually by a cookie blocker, an extension that modifies redirect URLs, or a browser that refuses to store the auth cookie after a successful verification. The loop repeats because each attempt generates a new token that expires after a single use, so re-clicking the same magic link always fails.
Common Mistakes to Avoid
- Clicking the magic link twice. Each email verification link is single-use and expires within 15 minutes. Clicking it twice—or forwarding it to another browser—will invalidate it. Always open the link in the same browser where you started the login flow.
- Using a work email with SSO restrictions. Many corporate email providers redirect authentication through their own SSO gateway, which can break the OAuth handshake. If your work email fails, try with a personal Gmail or Apple account.
- Leaving third-party cookie blocking enabled. Claude’s auth flow requires third-party cookies to be allowed for claude.ai. Browsers with strict tracking protection (Firefox Enhanced Protection, Safari Prevent Cross-Site Tracking) will block the session cookie and send you back to the login screen in a loop.
- Not checking for a Cloudflare or WAF block. Some network configurations trigger Cloudflare bot detection during login. If you see a "checking your browser" screen that never completes, switch to a mobile hotspot to bypass the corporate or ISP-level filter.
- Giving up before checking for a service outage. Login outages affecting all users occur occasionally. Check status.anthropic.com before spending time troubleshooting local settings.
Q: Why does the verification email never arrive? Verification emails from Anthropic are sent from a noreply@anthropic.com address and can be filtered by spam or corporate email gateways. Check your spam/junk folder first. If you use a corporate email, ask your IT team whether outbound links from anthropic.com are being rewritten or blocked by the email security gateway, which would invalidate magic links before you open them.
Q: The magic link works, but I’m immediately sent back to login. What causes this? This is the classic verification loop and is almost always caused by a blocked session cookie. After you click the magic link, Claude’s server sets a session cookie in your browser. If your browser blocks this cookie (strict privacy mode, ITP, or a cookie-blocking extension), the session is not persisted, and the next page load treats you as unauthenticated again. Enable cookies for claude.ai, or use an incognito window with extensions disabled.
Q: How can I log in if I no longer have access to my original email address? If you signed up with an email you can no longer access, you will need to contact Anthropic support directly. Provide your original email address, approximate account creation date, and any billing receipts. Anthropic can manually transfer account access, but this process requires identity verification and typically takes 2–5 business days.
Q: Does using a VPN affect the login verification? Yes, in some cases. Claude’s fraud detection may flag logins from certain VPN exit nodes, particularly shared datacenter IPs. If verification emails arrive but links fail, or if you see a CAPTCHA that does not complete, try logging in with the VPN disabled. Once logged in successfully, you can re-enable the VPN for normal use.
Q: I’m stuck in a loop only on mobile. Desktop works fine. Why? Mobile browsers apply stricter cookie policies than desktop browsers by default, especially Safari on iOS with Intelligent Tracking Prevention. Additionally, mobile browsers with built-in ad blocking (Brave, Firefox Focus) may strip the auth redirect parameters. Switch to Safari or Chrome on mobile, temporarily disable enhanced tracking protection, and retry the login.
Related Issues
- Claude cannot log in
- Claude access issues after switching devices
- Claude workspace access denied
- Claude subscription active but features locked
Additional FAQ
Q: What is the fastest way to diagnose a login problem? The fastest diagnostic is to open an incognito or private browser window and attempt to sign in there. Incognito windows run without extensions and use fresh cookies, which isolates the two most common causes: a browser extension interfering with authentication, or corrupted session cookies. If login works in incognito, the issue is your main browser profile. If it still fails, the problem is your network, your account, or a platform-side incident.
Q: Why does clearing browser cache fix login issues? Your browser caches session tokens and authentication cookies that prove you are logged in. If these become corrupted or expire mid-session, the browser may present an invalid token on each page load, causing the server to reject the session and redirect you to login. Clearing site-specific data forces the browser to request fresh tokens on the next login, which resolves most session-related loops without affecting your other browser data.
Q: Should I try a different browser if login keeps failing? Yes — testing in a second browser is one of the most useful steps. Different browsers use different cookie stores, extension ecosystems, and caching mechanisms. If login works in Browser B but fails in Browser A, the issue is specific to Browser A's state (likely extensions or corrupted profile data), not your account. You can continue working in Browser B while you troubleshoot the original browser.
Related Articles
- Claude usage limit reached
- Claude rate limit fix
- Claude blank page white screen
- Claude can't log in fix
Additional FAQ
Q: What is the fastest way to diagnose a login problem? The fastest diagnostic is to open an incognito or private browser window and attempt to sign in there. Incognito windows run without extensions and use fresh cookies, which isolates the two most common causes: a browser extension interfering with authentication, or corrupted session cookies. If login works in incognito, the issue is your main browser profile. If it still fails, the problem is your network, your account, or a platform-side incident.
Q: Why does clearing browser cache fix login issues? Your browser caches session tokens and authentication cookies that prove you are logged in. If these become corrupted or expire mid-session, the browser may present an invalid token on each page load, causing the server to reject the session and redirect you to login. Clearing site-specific data forces the browser to request fresh tokens on the next login, which resolves most session-related loops without affecting your other browser data.
Related Articles
- Claude usage limit reached
- Claude rate limit fix
- Claude blank page white screen
- Claude can't log in fix
Additional FAQ
Q: What is the fastest way to diagnose a login problem? The fastest diagnostic is to open an incognito or private browser window and attempt to sign in there. Incognito windows run without extensions and use fresh cookies, which isolates the two most common causes: a browser extension interfering with authentication, or corrupted session cookies. If login works in incognito, the issue is your main browser profile. If it still fails, the problem is your network, your account, or a platform-side incident.