Skip to main content

Let's Encrypt

Let's Encrypt is a Certificate Authority (CA) that provides automated issuance and renewal of domain-validated TLS/SSL certificates (web security / Public Key Infrastructure (PKI)) at no cost to enable HTTPS on websites and services.

  • Automated issuance and renewal of domain-validated TLS/SSL certificates via the ACME protocol (web security / PKI)
  • Support for standard X.509 digital certificates used for HTTPS and other TLS-based services (web security / PKI)
  • ACME-based integration with web servers, load balancers, and tooling for automated certificate lifecycle management (infrastructure automation / security)
  • Public root and intermediate certificates trusted by major browsers and operating systems (trust infrastructure / PKI)
  • Focus on encryption of Hypertext Transfer Protocol (HTTP) traffic to improve privacy and security on the public internet (web security)

More About Let's Encrypt

Let's Encrypt is a public CA operated by the Internet Security Research Group that issues domain-validated TLS/SSL certificates (web security / PKI) to enable encrypted HTTPS connections for websites and internet services. Its purpose is to make encrypted transport more accessible by providing certificates at no cost and by automating certificate management through open protocols.

The core technical foundation of Let's Encrypt is the Automated Certificate Management Environment (ACME) protocol (security automation / protocol), which defines how clients request, validate, issue, and renew certificates in an automated way. Using ACME, a client proves control over a domain name through HTTP or Domain Name System (DNS) challenges, after which Let's Encrypt issues an X.509 certificate (web security / PKI) that can be deployed to web servers, reverse proxies, content delivery platforms, or application gateways. Certificates are domain-validated only and are intended for server authentication and encryption rather than organization or extended validation use cases.

Enterprise and institutional environments commonly use Let's Encrypt certificates with web servers, Application Programming Interface (API) gateways, and load balancers to terminate Transport Layer Security (TLS) for public-facing services. Integration is supported through ACME-compatible clients and tooling (infrastructure automation / security), which can run on individual hosts or within orchestration frameworks to manage certificate issuance and renewal on a schedule. This automation reduces manual certificate operations and helps maintain continuous HTTPS availability with short certificate lifetimes.

Let's Encrypt operates a publicly trusted root and intermediate certificate hierarchy (trust infrastructure / PKI), which is embedded or trusted by major browser vendors, operating systems, and many network devices. This trust model allows clients to establish TLS connections without additional configuration when connecting to services that use Let's Encrypt certificates. The project publishes transparency information and participates in certificate transparency (observability / PKI) ecosystems by logging issued certificates to public Current Transformer (CT) logs, supporting auditability and monitoring of certificate issuance.

From a technical categorization perspective, Let's Encrypt fits into PKI, CA services, and TLS/HTTPS enablement for web and application workloads. Its focus on the ACME protocol ties it into a broader ecosystem of ACME clients, DNS providers, and hosting platforms that implement automated certificate workflows. For enterprise directories, it is positioned under web security, identity and access (server authentication), and infrastructure automation for certificate lifecycle operations, providing a CA endpoint that integrates programmatically with a range of platforms and environments.