Safari "Can't Establish a Secure Connection" or "Not Secure" on Mac
Safari says it can’t establish a secure connection to the server, or shows a “Not Secure” warning, when you open a website on your Mac.
Why: Safari is telling you the connection isn’t properly encrypted. That can happen because the site’s certificate is expired or invalid, the site uses outdated encryption (TLS 1.1 or earlier), or the page is plain unencrypted but asks for a password or card number. Most often the cause is on the website’s end — but a few things on your Mac are worth ruling out.
Fix 1: Don’t enter sensitive info — confirm the warning
- If you see “Not Secure” and the site is asking for a password or credit card number, stop — never enter it on that site.
- A “Not Secure” label generally means one of three things: the certificate is expired or illegitimate, the encryption is too weak (TLS 1.1 or earlier), or the page is simply unencrypted.
- If it’s a site you don’t fully trust, leave it. The safest fix is to not transmit sensitive data over an unsecured connection.
Fix 2: Reload and retry
- Reload with View > Reload Page (or Command-R) — a one-time handshake glitch can trigger the error.
- Quit Safari (Command-Q) and reopen it, then try the site again.
- Try the same site from another device on the same network. If it fails everywhere, the problem is the website, not your Mac.
Fix 3: Update macOS and contact the site owner
- Keep your Mac current via Apple menu > System Settings > General > Software Update — Safari’s security and TLS support update with macOS.
- If a trusted site keeps showing the warning, the fix is on their side: their server needs a valid certificate and modern encryption. Contact the website owner or administrator and let them know their site triggers a security warning in Safari.
FAQ
Is this my Mac’s fault or the website’s? Almost always the website’s — an expired certificate or old encryption. Confirm by loading it on another device (Fix 2).
Could my date and time cause it? A badly wrong system clock can make valid certificates look expired. Set System Settings > General > Date & Time to set automatically, then retry.
Sources: Apple Support — If you see a ‘Not Secure’ warning while browsing with Safari