What is an SSL certificate and how does it work?

Have you ever noticed the little padlock icon in your browser bar when visiting a website? That small symbol is a big deal in terms of online security.

It means that the website is protected by an SSL certificate, which is a digital safeguard that helps ensure your data stays safe from shady characters.

Whether you're a website owner, digital marketer, or casual internet user just trying to stay safe, understanding SSL certificates is essential.

In this post, we’ll explain what an SSL certificate is, how it works, why it matters, and what types are available. We'll try our best to use clear, non-technical language wherever possible.

What is an SSL certificate?

An SSL certificate (short for Secure Sockets Layer) is a digital certificate that helps encrypt data transferred between your web browser and a web server. This encryption helps prevent hackers or malicious third parties from intercepting sensitive data like credit card numbers, login credentials, or other forms of personal information.

Even though SSL has evolved into Transport Layer Security (TLS), most people still refer to it as SSL. In practice, SSL certificates now use TLS, but the term "SSL certificate" remains the industry standard.

An SSL certificate has two main purposes:

1. It authenticates the domain name of the website, verifying that the site belongs to the correct website owner.

2. It enables a secure, encrypted connection between the web server and the user’s web browser.

You can recognize a site is using SSL by the padlock icon, a web address that starts with "https" (rather than "http"), and other trust signals in the address bar.

Each SSL certificate includes:

• The verified domain name

• The expiration date

• The public key and matching private key

• The name of the certificate authority

Why is SSL important?

Cyberattacks are on the rise, and absolutely no one wants to have their personal data stolen. So, securing your website is non-negotiable. SSL certificates are one of the main ways to do this. They protect sensitive information during any kind of online transaction.

If your website handles credit card info, usernames, passwords, or personal information, SSL is a must. It encrypts data so that it can’t be read, even if it is somehow intercepted.

SSL also helps:

Build trust with your visitors

When visitors see the padlock icon and HTTPS in the address bar, it signals that the site is secure.

This visual cue builds confidence, especially when users are entering personal information or making an online transaction. SSL certification is especially important if you have an online store. It's one of the essential ecommerce website features we talk about in our ecommerce website features list PDF.

Trust is a key factor in user experience, and a secure site often results in more time spent on the page, lower bounce rates, and higher conversion rates.

Prevent identity theft and phishing sites

SSL certificates help verify that a site is legitimate and operated by a verified website owner. This makes it much harder for cybercriminals to create fake, malicious websites (known as phishing sites) that impersonate real businesses.

When SSL is properly installed, it acts as a digital passport, reducing the risk of users being tricked into sharing sensitive information like passwords or credit card numbers.

Ensure compliance with laws like GDPR and PCI-DSS

Data protection regulations such as the General Data Protection Regulation (GDPR) and the Payment Card Industry Data Security Standard (PCI-DSS) require websites to use adequate security measures when handling personal information or credit card info. An SSL certificate is one of the most basic, and essential, requirements for compliance, helping businesses avoid legal issues and penalties.

Improve your site’s Google ranking

Google has made it clear that HTTPS is a ranking signal in its algorithm. Websites with an SSL certificate are more likely to appear higher in search results compared to those without one. Aside from SEO benefits, search engines may label unsecured sites as “Not Secure,” which can discourage clicks and hurt your organic traffic. So, as well as securing your site and protecting your visitors, SSL helps increase visibility.

Sites without SSL may show a “Not Secure” warning in the address bar, which can instantly turn visitors away.

How does an SSL certificate work?

The magic happens during what's known as the SSL handshake:

1. A web browser tries to connect to a site with SSL.

2. The site’s web server sends its SSL certificate to the browser.

3. The browser checks that the certificate authority is trusted and that the certificate is valid.

4. A public key is used to encrypt data, while a private key decrypts it.

5. Once the handshake is complete, all data is transferred via an encrypted connection.

This process uses two types of encryption to keep your information safe:

Asymmetric encryption

This involves two separate keys: a public key and a private key. The public key is shared openly and used to encrypt data, while the private key is kept secret and used to decrypt that data.

• Think of it like a locked mailbox on a street corner:

• Anyone can drop in a message using the public key (like putting a letter in the mailbox).

Symmetric encryption

Once the connection is established, the server and browser agree on a temporary, shared secret key (called a session key) to encrypt the rest of the communication. This method is faster and more efficient for ongoing data transfer.

So, the SSL protocol uses the strengths of both methods: asymmetric encryption to safely exchange the session key, and symmetric encryption to protect the actual data being transmitted, like your credit card numbers, personal information, and other sensitive data. This combination ensures that even if someone intercepts the data, they won’t be able to read or misuse it.

Types of SSL certificates

To make things more confusing, there are multiple types of SSL certificates. Each type has a different level of security, so there are various use cases:

1. DV SSL (domain validation)

• Basic validation: only proves domain ownership.

• Quick to issue, ideal for personal blogs or small sites.

• Shows padlock icon, but not company name in the address bar.

2. OV SSL (organization validation)

• Confirms both domain ownership and business registration.

• Suitable for small-to-medium businesses.

• Adds business info to certificate, increasing trust.

3. EV SSL (extended validation)

• Highest trust level: validates full business identity.

• Used by banks, eCommerce, and enterprises.

• Used to show the business name in the address bar.

• Great for sites handling credit card and online transaction data.

Other formats include:

• Wildcard SSL certificate: Secures one single domain and all its subdomains.

• Multi-Domain SSL certificate: Secures multiple unrelated domains.

Whether you’re protecting a single domain or many, choosing the right type of certificate depends on your site’s structure and security needs.

How to get and install an SSL certificate

Getting an SSL certificate is easier than it sounds:

1. Decide which type of certificate you need (DV, OV, or EV).

2. Generate a Certificate Signing Request (CSR) from your web server.

3. Submit the CSR to a trusted certificate authority.

4. Once issued, install the certificate on your web server.

Some web hosts offer free certificates via Let’s Encrypt, while others resell from commercial providers. Paid certificates may include additional warranty or support.

Be sure to:

• Set up automatic renewal (to avoid expiration date issues)

• Force HTTPS redirects

• Check for mixed content errors

Tools like SSL Labs or “Why No Padlock?” can help you verify that your SSL certificate is properly installed.

Common SSL issues (and how to fix them)

Mixed content warnings (some files still load over HTTP)

When some parts of your site, like images, scripts, or stylesheets, still load over HTTP instead of HTTPS, browsers flag this as a security risk.

FIX: Update all resource URLs to use HTTPS. Most CMS platforms and plugins offer tools to help find and fix mixed content.

Incorrect or outdated digital signature

If the digital signature on your SSL certificate doesn’t match the expected cryptographic values, users may see a trust warning.

FIX: Reissue or replace your SSL certificate through your certificate authority, and ensure your server is updated to support the latest encryption standards.

An expired certificate (expiration date)

SSL certificates are only valid for a set period, usually 90 days to 1 year. Once the expiration date passes, browsers will block or warn users away from your site.

FIX: Renew your certificate before it expires. Set calendar reminders or enable auto-renewal with your hosting provider or certificate authority.

Misconfigured web server or redirect loop

Your web server must be set up correctly to serve the SSL certificate and redirect traffic from HTTP to HTTPS. A misconfiguration can cause redirect loops or failed secure connections.

FIX: Check your ht.access file, server settings, or CMS configuration to ensure redirects are correctly set. Use tools like SSL Labs to test the setup

Untrusted third-party certificate authority

If your certificate was issued by a third party that isn’t recognized by major browsers, users will see a trust error, even if the certificate is technically valid.

FIX: Only get SSL certificates from well-known, trusted certificate authorities like Let’s Encrypt, DigiCert, or Sectigo. Avoid unknown or self-signed certs for public websites.

SSL and the bigger picture of security

An SSL certificate is a foundational part of online security, but it’s not the only part. Combine it with:

• Secure hosting and firewalls

• Strong password policies

• Regular software updates

Also consider user-facing trust signals like:

• A clean design

• Clear privacy policy

• A visible padlock icon in the address bar

Together, these help build trust and protect your site from phishing sites, malware, and data leaks.

So, what is an SSL certificate and how does it work?

Well, an SSL certificate is about keeping your website and your visitors safe. It proves your site is legitimate, scrambles sensitive data so no one else can read it, and shows people they can trust you with things like their login credentials and credit card details.

Behind the scenes, it’s a team effort: the SSL handshake, the public and private keys, and the check from a trusted certificate authority all work together to create a secure connection.

Whether you’re setting up a full-blown online store or just running a personal blog on a single domain, SSL isn’t optional anymore. Pick the right type of certificate, go with a trusted provider, and make sure your web server is set up correctly.

Because when your site’s secure, your visitors feel secure too. And it all starts with an SSL certificate.

Frequently asked questions

What is SSL encryption, and why is it important?

SSL encryption scrambles data as it travels between your web server and a visitor’s browser, so it can’t be read by anyone who intercepts it. Without it, data is sent in plain text, which makes it easy for hackers to steal things like confidential information or credit card details. Encryption helps create a secure session, giving both you and your users peace of mind.

What does the green padlock mean in my browser?

The green padlock (now often just a padlock icon) that appears in the browser’s address bar indicates that the website has a valid SSL certificate and has established a secure connection. It’s a visual cue that your data is encrypted and that the site has passed a basic verification process by a trusted certificate authority.

What is a secure session?

A secure session is a protected connection between your browser and the web server, established using SSL encryption. It ensures that any information you send, such as login credentials or personal information, remains private and can’t be read or altered in transit.

Can I still send data without SSL?

Technically, yes, but it’s not safe. Without SSL encryption, all data you enter into a site is sent in plain text, which means it can be intercepted by cybercriminals. If you're sending or collecting confidential information, an SSL certificate is absolutely essential.

What is the SSL verification process?

The verification process depends on the type of certificate you choose. For a basic DV SSL, you only need to prove control over the domain name. For OV or EV SSL certificates, the certificate authority also verifies your business identity. Once verified, the certificate is issued, and your site can establish a secure session with visitors.

What happens if I don't have an SSL certificate?

If your website doesn’t have an SSL certificate, several things can go wrong:

• Visitors will see a “Not Secure” warning in the address bar, which can instantly damage trust and drive people away from your site.

• Any data sent to or from your site, like passwords, credit card info, or other confidential information, will be transmitted in plain text, making it easy for hackers to steal.

• Your site won’t have a secure session, so it’s vulnerable to man-in-the-middle attacks and other security threats.

• You could fail compliance requirements for regulations like GDPR or PCI-DSS, especially if you handle sensitive or payment data.

• Search engines like Google may rank your site lower in search results because SSL is now a known ranking factor.

In short, skipping SSL puts your users and your reputation at risk. It’s one of the simplest and most essential steps you can take to keep your site safe and credible.