Let's Encrypt
Let’s Encrypt is a free, automated, and open Certificate Authority (CA) run by the Internet Security Research Group (ISRG) that provides SSL/TLS certificates at no cost. Using the Automated Certificate Management Environment (ACME) protocol, it enables web servers to automatically obtain and renew certificates — eliminating the traditional barriers of cost, manual paperwork, and complex configuration. Since its launch in 2016, Let’s Encrypt has issued over a billion certificates, making HTTPS the default for millions of websites worldwide.
Key Features
- Fully automated certificates — No paperwork, no manual validation, no human intervention needed; the ACME client handles everything automatically
- Free of charge — Every certificate is completely free, making HTTPS accessible to everyone regardless of budget
- Automatic renewal — Certificates are valid for 90 days, and ACME clients handle renewal automatically before expiry, eliminating forgotten-renewal downtime
- Multiple validation methods — Supports HTTP-01 (webroot challenge), DNS-01 (TXT record challenge), and TLS-ALPN-01 for flexible deployment options
- Wildcard certificates — Single certificate covering a domain and all its subdomains (*.example.com) via DNS-01 validation
- Open standards — Built on ACME (RFC 8555), an IETF standard protocol that any ACME client or server can implement
- Widely trusted — Root certificates are cross-signed by IdenTrust and trusted by all major browsers, operating systems, and devices
- Transparent operations — All certificates are logged to Certificate Transparency (CT) logs, and the entire operation is publicly accountable
Why Use Let’s Encrypt?
Let’s Encrypt democratised HTTPS by removing the two biggest barriers: cost and complexity. Before Let’s Encrypt, an SSL certificate cost $50–$300/year and required manual renewal. Now, any site can get trusted certificates for free in seconds using tools like Certbot, and automation means you set it once and forget it. For site owners, it’s the easiest path to HTTPS — and Google’s ranking boost for HTTPS sites makes it a practical SEO advantage too.
Use Cases
- Personal websites and blogs — Secure your personal site with zero cost and minimal configuration using Certbot’s automatic nginx/Apache integration
- Small business e-commerce — Enable encrypted checkout and customer data protection without the recurring cost of paid certificates
- API and web service endpoints — Automatically provision and renew certificates for microservices, dev/staging environments, and internal tools with ACME DNS challenges
Platform
Any web server (nginx · Apache · Caddy · HAProxy · Traefik) · Linux · Docker · BSD · macOS
Licence
Server-side: ISG/ISC-style (open-source CA operations). Client tools (Certbot, acme.sh, etc.): Apache 2.0 / GPL 3.0