Quick Summary
The "SEC_ERROR_UNKNOWN_ISSUER" error in Chrome indicates that your browser doesn't trust the SSL certificate presented by a website because it cannot verify the issuing Certificate Authority (CA). This usually means the certificate is self-signed, issued by an untrusted CA, or the certificate chain is incomplete.
Common Causes
- Self-Signed Certificate: The website is using a certificate that wasn't issued by a trusted Certificate Authority. Self-signed certificates are commonly used on internal or development sites, but are not trusted by browsers by default.
- Untrusted Certificate Authority: The certificate was issued by a CA that Chrome doesn't recognize or trust. This can happen with less common or newly established CAs.
- Incomplete Certificate Chain: The server didn't provide the full chain of certificates needed to verify the certificate's authenticity. Browsers need the intermediate certificates to trace back to a trusted root CA.
- Outdated Browser or Operating System: Your browser or operating system might not have the latest root certificates installed, preventing it from trusting certain CAs.
- Security Software Interference: Antivirus or other security software can sometimes interfere with SSL certificate verification, causing this error.
- Man-in-the-Middle Attack: Although less likely, a malicious actor could be intercepting your connection and presenting a fake certificate. Be cautious if you encounter this error frequently on different websites.
Step-by-Step Fixes
Method 1: Proceed with Caution (Temporary Workaround - Not Recommended)
Warning: This is not a recommended solution as it bypasses security warnings and could expose you to risks. Only use this on sites you trust completely and understand the risks involved.
Step 1: Click on "Advanced" on the error page.
Step 2: If available, click on the link to proceed to the website (e.g., "Proceed to example.com (unsafe)").
Method 2: Add the Certificate Exception (Temporary Workaround - Not Recommended)
Warning: This solution adds a permanent exception for the certificate. Only use it if you completely trust the site and are aware of the risks. This should never be used for banking, email, or social media sites.
Step 1: Click on "Advanced" on the error page.
Step 2: Look for an option to add an exception for the certificate. The wording might vary (e.g., "Add Exception...").
Step 3: Follow the prompts to add the certificate exception.
Method 3: Update Chrome and Operating System
Step 1: In Chrome, click on the three vertical dots in the top-right corner.
Step 2: Go to "Help" > "About Google Chrome".
Step 3: Chrome will automatically check for updates and install them. Restart Chrome if prompted.
Step 4: Update your operating system to the latest version as well (e.g., Windows Update, macOS System Preferences > Software Update).
Method 4: Check Date and Time Settings
Step 1: Ensure your computer's date and time are set correctly. Incorrect date/time settings can interfere with SSL certificate validation.
Step 2: Set your date and time to synchronize automatically with an internet time server.
Method 5: Clear SSL State in Chrome
Step 1: Go to Chrome Settings (chrome://settings/).
Step 2: Search for 'proxy settings'.
Step 3: Open your system's proxy settings (this will open your operating system's network settings).
Step 4: Go to the 'Content' tab, and then press 'Clear SSL state'.
Step 5: Restart Chrome.
Note: The user interface could look different depending on your operating system and its version.
Method 6: Disable Antivirus/Firewall Temporarily (For Testing Purposes Only)
Warning: Only disable your antivirus or firewall temporarily for testing purposes. Re-enable it immediately after testing.
Step 1: Temporarily disable your antivirus or firewall software.
Step 2: Try accessing the website again. If the error is resolved, your security software is likely interfering with the SSL certificate verification. Configure your antivirus/firewall to allow the website's traffic or exclude it from SSL scanning.
Method 7: Contact Website Administrator
If the problem persists, especially if it occurs on a website you trust, contact the website administrator. They may need to update their SSL certificate, fix an incomplete certificate chain, or address other server-side issues.