cert-manager vs Let's Encrypt

cert-manager is a free, open-source tool for obtaining and managing X.509 certificates on Kubernetes and OpenShift. It requests certificates from public or private issuers, keeps them valid, and attempts renewal before expiration. The project automates TLS certificate issuance for Kubernetes Ingress and supports private-PKI certificates for pod-to-pod mutual TLS. Documented authority options include Let’s Encrypt, HashiCorp Vault, CyberArk Certificate Manager, and private PKI. Installation can use kubectl-applied manifests, Helm, Flux, or Argo CD. Related projects include istio-csr, approver-policy, Kubernetes CSI drivers, csi-driver-spiffe, and trust-manager; trust-manager distributes X.509 trust bundles and can run independently. cert-manager publishes threat-model and hardening guidance covering secrets, RBAC, networking, and Kubernetes configuration. Its default Helm values prioritize installation ease and backward compatibility over hardened production security. The project has no LTS releases, though each release is supported until the second subsequent version.

Let’s Encrypt is a global Certificate Authority that provides SSL/TLS certificates for HTTPS connections. The ACME protocol verifies control of a domain, and compatible clients can automate issuance, management, and renewal. Its client directory includes Apache HTTP Server, Caddy, nginx, Kubernetes, Docker, and Windows/IIS environments. Certificates are Domain Validation only; Let’s Encrypt says it does not plan to issue Organization Validation or Extended Validation certificates. Wildcard certificates are available through the DNS-01 challenge. Standard certificates last 90 days, with an optional six-day lifetime; these periods cannot be adjusted. Subscribers generate and manage private keys on their own servers. Issued and revoked certificates are publicly recorded, and the service says its certificates are trusted by most browsers and operating systems. Certificates cost nothing. A registered domain can receive up to 50 certificates every seven days under published rate limits. Direct subscriber support is not offered.