Security

How to Fix SSL Certificate Errors (Complete 2026 Guide)

Published 2026-03-26 · 5 min read

Common SSL Errors and What They Mean

NET::ERR_CERT_DATE_INVALID - Certificate expired
NET::ERR_CERT_AUTHORITY_INVALID - Untrusted CA
NET::ERR_CERT_COMMON_NAME_INVALID - Domain mismatch
Mixed Content - HTTP resources on HTTPS page

How to Fix Each Error

Expired Certificate:
1. Renew with your CA or Let's Encrypt
2. Install the new certificate
3. Update auto-renewal settings

Chain Issues:
1. Download intermediate certificates
2. Install in correct order
3. Test with SSL checker

Mixed Content:
1. Find HTTP resources in source
2. Update to HTTPS or use protocol-relative URLs
3. Add upgrade-insecure-requests CSP

Test Your Fix

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