HSTS (HTTP Strict Transport Security)
An HTTP response header that tells browsers to only ever connect to your site over HTTPS — protects against SSL-stripping attacks. Best practice: `max-age=31536000; includeSubDomains; preload`.
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Related terms
SSL / TLS
Transport Layer Security (TLS) is the cryptographic protocol that powers HTTPS.
TLS 1.2 vs TLS 1.3
TLS 1.3 (2018) is faster (one round-trip handshake) and more secure (removed legacy ciphers) than TLS 1.2.
TLS Certificate (Leaf, Intermediate, Root CA)
An X.509 certificate is a signed document binding a public key to a domain.
Certificate Chain
The sequence of certificates linking your server's leaf cert back to a trusted root CA.
Wildcard Certificate
A TLS cert valid for one subdomain level — `*.example.com` covers `api.example.com` but NOT `v2.api.example…
Let's Encrypt
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