Certificate Authority (CA) Explained

Reading time: 5 min

What is a Certificate Authority (CA)?

A Certificate Authority (CA) is a trusted organization responsible for issuing, validating, and managing SSL/TLS certificates.

Think of a CA as the trusted third party that confirms a website really belongs to the business or organization claiming ownership.

Without Certificate Authorities, browsers would have no reliable way to know whether a website is legitimate.

Why Certificate Authorities Exist

Imagine receiving an ID card without knowing who issued it.

Would you trust it?

Probably not.

The same principle applies to SSL certificates.

Certificate Authorities verify identities before issuing certificates, allowing browsers to trust secure websites.

What Does a Certificate Authority Do?

A Certificate Authority:

Verifies domain ownership
Verifies business identity (OV & EV certificates)
Issues SSL certificates
Maintains Certificate Revocation Lists (CRLs)
Protects the trust chain of the internet

How Certificate Authorities Work

The process typically follows these steps:

1. Certificate Request

A website owner requests an SSL certificate.

↓

2. Identity Validation

The CA verifies:

Domain ownership
Business registration (OV/EV)
Organization information

↓

3. Certificate Issued

Once verification is complete, the SSL certificate is digitally signed by the CA.

↓

4. Browser Trust

When visitors connect, browsers verify that the certificate was issued by a trusted Certificate Authority.

If everything checks out, a secure HTTPS connection is established.

Popular Certificate Authorities

Some of the world's most trusted Certificate Authorities include:

DigiCert
Sectigo
GlobalSign
Entrust
GeoTrust
Thawte
RapidSSL
Let's Encrypt

These CAs are trusted by major browsers including Chrome, Edge, Firefox, and Safari.

Root vs Intermediate Certificate Authorities

Most Certificate Authorities operate using two levels of trust:

Root CA

The highest level of trust.

Stored directly in browsers and operating systems.

Intermediate CA

Used to issue website certificates while protecting the Root Certificate from exposure.

This creates the Certificate Chain that browsers validate.

What Happens if a CA Isn't Trusted?

If a certificate comes from an unknown or untrusted Certificate Authority, browsers may display warnings such as:

Your connection is not private
Certificate not trusted
NET::ERR_CERT_AUTHORITY_INVALID

Visitors are likely to leave the site immediately.

Choosing the Right Certificate Authority

When selecting an SSL certificate, consider:

Browser compatibility
Reputation
Validation options (DV, OV, EV)
Warranty
Customer support
Certificate management tools

A trusted CA helps ensure maximum browser compatibility and user confidence.

Frequently Asked Questions

Are all Certificate Authorities trusted?

No.

Browsers maintain a list of approved Root Certificate Authorities. Certificates issued by unknown CAs are generally rejected.

Can anyone become a Certificate Authority?

Technically yes, but becoming publicly trusted by browsers requires meeting strict security, auditing, and compliance requirements.

Does the CA encrypt my website?

No.

The CA issues and signs the certificate. Encryption occurs between the visitor's browser and your web server using TLS.