---
title: "SSL/TLS (Secure Sockets Layer / Transport Layer Security)…"
description: "SSL/TLS is the cryptographic protocol that secures HTTPS connections. It encrypts traffic between browser and server, authenticates the server's identity via…"
canonical: "https://lemwatch.com/glossary/ssl"
source: "https://lemwatch.com"
---

# SSL/TLS (Secure Sockets Layer / Transport Layer Security)

> SSL/TLS is the cryptographic protocol that secures HTTPS connections. It encrypts traffic between browser and server, authenticates the server's identity via a certificate, and ensures message integrity. SSL is the deprecated name; modern deployments use TLS…

## Definition

 Each HTTPS site presents a certificate signed by a trusted Certificate Authority (CA). Browsers verify the signature chain and reject connections to expired, mismatched, or unsigned certificates with a full-screen warning that destroys conversion rate.

 Certificates have expiry dates (typically 90 days for Let's Encrypt, 1-2 years for paid CAs). Forgetting to renew is one of the most common causes of preventable downtime — even at large companies.

## Why it matters

 An expired certificate makes a site appear broken to every visitor. Monitoring certificate expiry with multi-week lead time, plus alerting on TLS configuration regressions (weak ciphers, missing OCSP stapling), is essential for any production site.

 See it in the product: [SSL monitoring](https://lemwatch.com/features).


## Related

- [Monitoring glossary](https://lemwatch.com/glossary)
- [Security Headers](https://lemwatch.com/glossary/security-headers)
- [HSTS](https://lemwatch.com/glossary/hsts)
- [CSP](https://lemwatch.com/glossary/csp)
- [All monitoring checks](https://lemwatch.com/features)
- [Status Page](https://lemwatch.com/glossary/status-page)
- [SPF (Sender Policy Framework)](https://lemwatch.com/glossary/spf)