An SSL certificate (technically a TLS certificate) is a digital file, signed by a trusted certificate authority, that proves a website's identity and lets browsers set up an encrypted HTTPS connection.
An SSL certificate is a small digital file that proves your website is really yours and lets browsers make an encrypted HTTPS connection to it. It's issued by a trusted certificate authority and has an expiry date. When it's valid, visitors see the padlock. When it's expired or wrong, browsers show a full-page warning.
The padlock next to your web address comes from an SSL certificate. It's simple to get right, and when it goes wrong, every visitor sees it.
How does an SSL certificate work?
A certificate contains your domain name, a public key, an expiry date, and a digital signature from a certificate authority, the trusted company that issued it. Before issuing, the authority checks that you control the domain. Let's Encrypt, for example, asks your server to publish a specific file or DNS record to prove it.
When a visitor opens your site, their browser checks three things: the certificate was issued by an authority it trusts, it matches the address being visited, and it hasn't expired. If all three pass, the browser sets up an encrypted connection and shows the padlock.
Why does an SSL certificate matter for small businesses?
Without a valid certificate, browsers label your site "Not secure" or block it with a warning page. Contact forms, logins and checkout pages can't be trusted, and customers notice.
The most common problem is an expired certificate, not a missing one. Most hosts renew automatically, but renewals can fail quietly after a DNS or hosting change, and nobody finds out until a customer mentions it.
How do I check or set up an SSL certificate?
Run our free SSL checker. It shows who issued your certificate, when it expires, and whether browsers trust it.
If you don't have one, look for an SSL, HTTPS or Security setting in your hosting or website builder dashboard and switch on the free certificate. Then turn on "Force HTTPS" so every visitor gets the encrypted version.
If yours has expired, our guide to an expired SSL certificate walks through renewing it. If browsers say your site is "Not secure" for another reason, see why a website says Not Secure.
SSL vs TLS
SSL was the original technology. TLS replaced it years ago, and today's certificates are used with TLS. The names are used interchangeably, so an "SSL certificate" from your host is a TLS certificate. Once HTTPS works, HSTS can tell browsers to always use it.
A free CyberVigil scan checks your certificate, HTTPS redirect and encryption versions together.
Common questions
Do I have to pay for an SSL certificate?
Usually not. Let's Encrypt issues free, browser-trusted certificates, and most hosts and website builders include a free certificate that renews automatically. Paid certificates mainly add support or extra validation.
What happens when an SSL certificate expires?
Browsers show a full-page security warning instead of your website, and most visitors leave. Forms and checkout stop feeling safe to use. Renewing or reissuing the certificate fixes it right away.
Is SSL the same as TLS?
Almost. TLS is the modern version of SSL, and every current certificate is really a TLS certificate. The name SSL stuck around, so most hosts still call it an SSL certificate.
Sources
- Digital Certificate (glossary) (NIST Computer Security Resource Center)
- How It Works (Let's Encrypt)
Related guides and tools
Keep building a safer business
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