Every time a customer types a password, a card number, or an address into your website, that information travels across networks you don’t control. An SSL\/TLS certificate is what lets the browser encrypt that trip and check that it is really talking to your site.<\/p>\n
This guide explains in plain words what a certificate is, how HTTPS protects data in transit, what it doesn’t protect, which type to choose, and how to avoid the problems that catch site owners out, such as expired certificates and mixed content. If you run your own server, you can pair it with our guide to what a VPS is and how it works<\/a>.<\/p>\n An SSL\/TLS certificate is a digital file installed on your web server. According to Cloudflare’s explanation<\/a>, it proves your site’s identity and gives browsers the public key they need to start an encrypted connection. The matching private key stays secret on your server.<\/p>\n A certificate contains:<\/p>\n SSL is the older name. The protocol in use today is TLS, which replaced it, but people still say “SSL certificate” for both. Any site that loads over an HTTPS address uses SSL\/TLS, so when you buy or install an “SSL certificate”, you are getting a certificate that works with TLS. This guide uses “SSL\/TLS” so you can recognize both terms.<\/p>\n Strictly speaking, the certificate itself does not encrypt anything. The TLS protocol does the encrypting, and the certificate proves who you are and makes the key exchange possible.<\/p>\n When a customer opens your site over HTTPS, the browser and server run a short exchange called the TLS handshake before any page content is sent. Cloudflare describes it<\/a> in these steps:<\/p>\n After the handshake, the page, the form fields, and the cookies all travel under those session keys.<\/p>\n In plain terms, a person on the same Wi-Fi network or along the route can see that a customer connected to your site, but not what they typed or received.<\/p>\n A certificate protects data while it moves. It does not make a site or a server safe. Being clear about this keeps you from over-promising to customers.<\/p>\nWhat Is an SSL\/TLS Certificate?<\/h2>\n
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SSL vs TLS<\/h3>\n
A Certificate Does Two Jobs<\/h3>\n
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How HTTPS Protects Data in Transit<\/h2>\n
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Two Kinds of Encryption, Two Jobs<\/h3>\n
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What SSL\/TLS Protects, and What It Doesn’t<\/h2>\n