Security
Let's Encrypt
Also known as: Certbot
A free certificate authority — paired with the Certbot tool — that automatically issues and renews the TLS certificates that serve a site securely over HTTPS.
Let's Encrypt is a free, automated certificate authority. It issues the TLS certificates that put the padlock in the browser and let a site be served over HTTPS — at no cost, and without the manual back-and-forth that obtaining certificates used to require.
Certbot is the companion tool that automates the process: it requests a certificate from Let's Encrypt, proves the server controls the domain, installs the certificate, and — critically — renews it automatically before it expires. Let's Encrypt certificates are short-lived by design (90 days), so automated renewal is not a nicety, it is the whole point. Set up correctly, the site simply stays secured with no human intervention.
Together they made encrypted-by-default the norm. The thing to get right is the auto-renewal: a misconfigured renewal is invisible until the certificate quietly expires and visitors hit security warnings — exactly the kind of failure proper setup prevents.