TLS vs SSL: What Is the Difference?
SSL and TLS are often used interchangeably but mean different things. TLS is the modern successor to SSL. Here is what you need to know.
TLS vs SSL: What Is the Difference?
The terms SSL and TLS are used interchangeably in everyday conversation — people say "SSL certificate" when they mean "TLS certificate" — but they refer to different versions of the same underlying protocol family.
The History
SSL (Secure Sockets Layer) was the original protocol developed by Netscape in the mid-1990s for encrypting web traffic.
| Version | Year | Status |
|---|---|---|
| SSL 1.0 | 1994 | Never released publicly (had flaws) |
| SSL 2.0 | 1995 | Deprecated in 2011, broken by DROWN attack |
| SSL 3.0 | 1996 | Deprecated in 2015, broken by POODLE attack |
TLS (Transport Layer Security) replaced SSL as the standardized version, developed by the IETF.
| Version | Year | Status |
|---|---|---|
| TLS 1.0 | 1999 | Deprecated in 2021 — do not use |
| TLS 1.1 | 2006 | Deprecated in 2021 — do not use |
| TLS 1.2 | 2008 | Current — widely supported, acceptable |
| TLS 1.3 | 2018 | Current — recommended, faster and more secure |
Why Do People Still Say SSL?
The term "SSL certificate" stuck even though every modern certificate uses TLS. Certificate Authorities still call them SSL certificates for marketing familiarity. The underlying standard is TLS — the certificate format (X.509) has not changed significantly.
When someone says "install an SSL certificate," they mean configure TLS on your web server. When someone says "SSL expired," they mean the TLS certificate expired.
Key Improvements in TLS 1.3
TLS 1.3 made major improvements over TLS 1.2:
- Faster handshake — 1-RTT (one round trip) instead of 2-RTT, with 0-RTT resumption for returning connections
- Forward secrecy required — all handshakes use ephemeral keys (ECDHE), so past sessions cannot be decrypted if the private key is later compromised
- Removed legacy cruft — RC4, MD5, SHA-1, DES, 3DES, and other weak algorithms were completely removed from the spec
- Simplified cipher suites — only 5 cipher suites are defined, all strong
What You Should Have
- Disable: SSL 2.0, SSL 3.0, TLS 1.0, TLS 1.1
- Keep: TLS 1.2 (for compatibility with older clients)
- Prefer: TLS 1.3 for all new connections
Use ElasticDomain's TLS Auditor tool to check what protocol versions and cipher suites your server currently accepts.
What About HTTPS?
HTTPS is just HTTP over TLS. The padlock in a browser means the connection uses TLS (not SSL, despite what the padlock icon implies historically). HTTPS does not indicate who owns the domain — it only indicates the traffic is encrypted.