Published 2022-05-20 by TechNet New England
When your browser shows "Your connection is not private" with a warning about security certificates, it means the website's SSL/TLS certificate has a problem. Your browser is protecting you from connecting to a potentially insecure site. ## What This Error Means The warning appears when: The website's certificate has expired. The certificate does not match the website's domain name. The certificate was issued by an untrusted authority. Your computer's date and time are wrong (causing valid certificates to appear expired). A network device (like a corporate proxy or captive portal) is intercepting the connection. ## Common Error Codes **NET::ERR_CERT_DATE_INVALID**: The certificate has expired or your computer's clock is wrong. **NET::ERR_CERT_COMMON_NAME_INVALID**: The certificate was issued for a different domain name. **NET::ERR_CERT_AUTHORITY_INVALID**: The certificate was issued by an untrusted authority. **SEC_ERROR_EXPIRED_CERTIFICATE** (Firefox): Same as the date invalid error. ## Fix 1: Check Your Computer's Date and Time This is the most common cause on individual computers. **Windows:** 1. Right-click the clock in the taskbar. 2. Select **Adjust date and time**. 3. Make sure **Set time automatically** is turned on. 4. Click **Sync now** under "Synchronize your clock." **Mac:** 1. Open **System Settings > General > Date and Time**. 2. Make sure **Set date and time automatically** is enabled. If your clock was wrong and you fix it, refresh the browser page. ## Fix 2: Try a Different Browser Open the same website in a different browser (Chrome, Edge, Firefox, Safari). If it works in one browser but not another, the issue is with the browser, not the website. ## Fix 3: Clear Browser Cache and Cookies An old cached certificate can cause this error even after the website has renewed it. **Chrome/Edge:** Press Ctrl + Shift + Delete (Windows) or Command + Shift + Delete (Mac). Check "Cached images and files" and "Cookies." Click Clear data. **Safari:** Go to Safari > Settings > Privacy > Manage Website Data > Remove All. **Firefox:** Press Ctrl + Shift + Delete. Select "Cache" and "Cookies." Click Clear Now. ## Fix 4: Check If You Are on a Captive Portal If you are on a hotel, airport, or coffee shop Wi-Fi, the network may require you to sign in through a web portal before allowing secure connections. Open a new browser tab and try visiting a plain HTTP website like **http://neverssl.com**. If the captive portal redirect works, sign in to the network, then try the original website again. ## Fix 5: Disable VPN or Proxy Temporarily Some VPNs and web proxies can interfere with SSL certificates. Temporarily disconnect your VPN or disable your proxy and try the website again. ## When to Proceed Anyway (and When Not To) **When it is safe to proceed:** If you are trying to access a device on your own network (like a router, NAS, or printer interface) that uses a self-signed certificate, you can click "Advanced" and "Proceed" safely. **When it is NOT safe:** If you are visiting a public website (especially banking, email, shopping, or any site where you enter a password), do NOT proceed past the warning. The certificate issue could indicate a man-in-the-middle attack. ## If You Manage the Website If you own or manage the website showing this error, the certificate likely needs to be renewed. Check your SSL certificate provider or hosting panel. Let's Encrypt certificates expire every 90 days and should auto-renew. If auto-renewal failed, renew manually and restart your web server. ## When to Contact IT If this error appears on multiple websites or on a managed work computer, contact your IT provider. It could indicate a network security device intercepting traffic, an expired internal certificate, or a system configuration issue.