# What is SSL/TLS?

> SSL/TLS is the encryption protocol that secures the connection between a visitor's browser and the server hosting the site, symbolised by the padlock and the HTTPS prefix in the address bar.

- Source canonique : [https://allaux.fr/en/glossaire/ssl-tls](https://allaux.fr/en/glossaire/ssl-tls)
- Langue : EN
- Dernière mise à jour : 2026-09-30

## Why it's essential for an online store

Without encryption, data exchanged between the visitor and the site (login credentials, address, information sent through the checkout) can be intercepted in plain text. SSL/TLS encrypts these exchanges. Its absence also has consequences beyond pure security: browsers show a “not secure” warning on HTTP sites, which hurts trust and conversion, and search engines use HTTPS as a ranking signal.

## In practice

An SSL/TLS certificate is now most often obtained for free via Let's Encrypt, generally provided and automatically renewed by the host. A common issue once the certificate is set up is “mixed content”: some resources on the page (images, scripts) continue to be loaded over HTTP, which stops the padlock from displaying correctly despite a valid certificate.

## A certificate that's usually free

> Thanks to authorities like Let's Encrypt, getting and renewing an SSL/TLS certificate generally no longer requires a purchase or regular manual intervention.

## FAQ

### Are SSL and TLS the same thing?

TLS is the current, secure version of the protocol; SSL is its predecessor, now obsolete. The term “SSL” is still used out of habit to refer to HTTPS encryption in general.

### Does an SSL/TLS certificate cost money?

Not necessarily: authorities like Let's Encrypt issue free certificates, commonly offered by default by most hosts.

### Why doesn't the padlock appear even though the certificate is properly installed?

It's often a mixed content issue: some resources on the page are still loaded over HTTP rather than HTTPS, which stops the browser from showing a full padlock.