Web Technologies

What Is an SSL Certificate?

Nov 23, 2025•14 min
#ssl#https#encryption#security#web-security#certificate

What Is an SSL Certificate?

Introduction

In today’s digital landscape, security is no longer optional — it is essential. When you open a website and see a padlock icon or the HTTPS protocol in the address bar, it means the site is secured with an SSL certificate. This certificate ensures that communication between you and the website is encrypted and protected from attackers.

From online banking to e-commerce purchases, from login forms to personal data submissions, SSL (and its successor TLS) forms the backbone of secure communication on the internet.

In this comprehensive guide, we explain what an SSL certificate is, how it works, the different types, how it affects SEO, why HTTPS is mandatory and why every modern website must have SSL.

What Is an SSL Certificate?

SSL (Secure Sockets Layer) is a security protocol that encrypts data transmitted between a user and a web server. Although the modern version is called TLS, the industry still commonly refers to it as “SSL”.

What SSL does:

  • encrypts data
  • creates a secure communication tunnel
  • prevents unauthorized access
  • ensures data integrity
  • verifies the identity of the website owner

Protected data includes:

  • login passwords
  • credit card information
  • personal identity data
  • form submissions
  • cookies
  • session tokens

Without SSL, this information can be intercepted or manipulated.

What Is HTTPS?

Once SSL is installed on a website, the site uses the HTTPS protocol.

HTTPS = Hyper Text Transfer Protocol Secure

While HTTP transmits information in plain text, HTTPS encrypts it.

Modern browsers:

  • show a padlock icon
  • display “Secure” for HTTPS
  • show “Not Secure” warnings for HTTP

Google Chrome, Safari, Firefox and Edge now flag non-HTTPS sites as unsafe.

How Does SSL Work?

SSL uses a combination of asymmetric encryption and symmetric encryption to establish a secure connection.

Here is how the process works:

1. User connects to an HTTPS website

The browser requests the site’s SSL certificate.

2. The server sends its SSL certificate

The certificate includes:

  • domain name
  • certificate authority (CA)
  • expiration date
  • public key
  • digital signatures

3. Browser validates the certificate

The browser checks whether the certificate:

  • is issued by a trusted CA
  • matches the domain name
  • is not expired
  • has not been tampered with

4. The browser generates a session key

This key is encrypted using the public key from the certificate.

5. The server decrypts the key

Using its private key, the server decrypts the session key.

Result:

Both sides now share the same secret key, forming a fully encrypted communication tunnel.

Despite sounding complex, this entire process happens in milliseconds.

Types of SSL Certificates

SSL certificates are categorized based on their level of validation.

1. DV SSL (Domain Validation)

  • the simplest and fastest type
  • only domain ownership is verified
  • ideal for personal websites, blogs and simple projects

Advantages:

  • issued within minutes
  • free versions available (Let’s Encrypt)

2. OV SSL (Organization Validation)

  • verifies the details of the company
  • displays organization information
  • suitable for business websites and corporate pages

3. EV SSL (Extended Validation)

  • the highest level of verification
  • requires official business documentation
  • used by banks, financial institutions and large e-commerce platforms

EV SSL certificates provide maximum trust and credibility.

SSL Certificate Files

When installing an SSL certificate, you typically encounter files such as:

  • Private Key → the server’s secret key
  • CSR (Certificate Signing Request) → request file
  • CRT → the actual certificate
  • CA Bundle → certificate chain from the issuer

These elements together enable secure communication.

Benefits of SSL Certificates

SSL certificates offer several advantages:

✔ Data encryption

Prevents eavesdropping and data theft.

✔ User trust

The padlock symbol increases user confidence.

✔ SEO benefits

Google ranks HTTPS sites higher than HTTP sites.

✔ Security compliance

Many APIs, browsers and payment systems require HTTPS.

✔ Protects data integrity

Ensures transmitted data is not modified.

SSL and SEO

Google officially confirmed that:

HTTPS is a ranking signal.

This means that having SSL improves search engine rankings.

Additionally:

  • users trust HTTPS sites more
  • browsers warn users against HTTP
  • HTTP leads to higher bounce rates

For e-commerce and membership-based websites, SSL is absolutely mandatory.

Where Is SSL Used?

SSL is used across all modern internet services:

  • websites and landing pages
  • admin panels
  • web APIs
  • mobile applications
  • payment systems
  • email services
  • server-to-server communication
  • IoT devices

Essentially, any system that sends or receives data requires SSL.

Free SSL Certificates (Let’s Encrypt)

Let’s Encrypt, backed by tech giants like Google and Mozilla, provides free SSL certificates.

Advantages:

  • totally free
  • widely supported
  • renews every 90 days
  • automatic renewal possible
  • compatible with all major browsers

Most hosting providers now offer automatic Let’s Encrypt installation.

Premium SSL Certificates

Paid certificates offer higher validation and additional security.

Popular providers:

  • DigiCert
  • Comodo
  • GeoTrust
  • GlobalSign
  • RapidSSL

Premium SSL offers:

  • stronger warranties
  • extended validation
  • liability insurance
  • priority support

It is often preferred by large businesses.

Mixed Content Warning

Mixed content occurs when an HTTPS site loads resources via HTTP.

Example:

  • website is HTTPS
  • images or scripts load from http://

This causes:

  • browser warnings
  • reduced trust
  • SEO penalties
  • blocked resources

To avoid this, all resources must load using HTTPS.

Certificate Renewal

SSL certificates must be renewed:

  • every 90 days (Let’s Encrypt)
  • every 1–2 years (premium SSL)

If expired:

  • the site becomes insecure
  • browsers block access
  • Google rankings drop

Timely renewal is essential.

Why Is SSL Mandatory Today?

A website without SSL:

  • is marked as “Not Secure”
  • loses user trust
  • may be blocked by payment providers
  • experiences lower SEO performance
  • risks data leaks

Modern browsers and users expect secure websites.

Thus:

SSL is not optional — it is a requirement.

Conclusion

SSL certificates form the foundation of modern web security. They encrypt communication, protect user data, ensure authenticity and provide trust. Whether it’s a small personal blog or a large-scale enterprise platform, every website must use SSL.

In this guide, we explained:

  • what SSL is
  • how HTTPS works
  • SSL validation types
  • the encryption mechanism
  • SEO benefits
  • free and premium options
  • certificate renewal
  • browser behavior

In today’s digital world, a professional website begins with a secure HTTPS connection powered by a valid SSL certificate.