Certificate Authority

Certificate authority↗ (CA) is a trusted organization that issues digital certificates, verifying that a website or service is who it claims to be and enabling encrypted HTTPS connections. When a browser connects to a site, it checks that the site's certificate was signed by a CA it trusts before showing the padlock icon.

This system underpins trust across the web: if a CA were compromised or issued a certificate to the wrong party, attackers could impersonate legitimate sites. That's why browsers maintain strict lists of trusted CAs and why certificate mis-issuance is treated as a serious incident.