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Let's Encrypt
LinkedIn lists San Francisco, California as ISRG headquarters.
What it is
Let’s Encrypt is a Certificate Authority that issues SSL/TLS certificates for secure HTTPS connections. Its ACME protocol verifies control of a domain, and compatible clients can automate certificate management and renewal. The client directory includes environments such as Apache HTTP Server, Caddy, nginx, Kubernetes, Docker and Windows/IIS. 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, but issuance requires the DNS-01 challenge. Certificates are free. The default lifetime is 90 days, with an optional six-day lifetime; subscribers cannot adjust either duration. Private keys are generated and managed on subscribers’ servers rather than stored by Let’s Encrypt. Issued and revoked certificates are publicly recorded for inspection. Let’s Encrypt says its certificates are trusted by most browsers and operating systems. A registered domain can receive up to 50 certificates every seven days, subject to published rate limits. Direct subscriber support is not offered; users are pointed to documentation and community forums. The service is available for people and organizations worldwide with domain-named servers, including web, mail and FTP servers.
For and against
For
- Certificates are free
- Clients can automate certificate management and renewal
- Wildcard certificates are available
- Private keys remain on subscribers’ own servers
Against
- Certificates are Domain Validation only
- Wildcard issuance requires the DNS-01 challenge
- Direct subscriber support is not offered
The verdict
Let’s Encrypt provides free DV certificates with automated management available through compatible clients. Readers should account for fixed certificate lifetimes and the service’s rate limits.
Who it suits
Let’s Encrypt suits people and organizations that need certificates for domain-named web, mail or FTP servers and can use compatible clients to automate management.
Plans and prices
Let's Encrypt certificates
Domain Validation certificates · default 90-day validity · automatic renewal through ACME clients
Read 15 Oct 2026 · letsencrypt.org
Short-lived certificates
Six-day validity · renewal recommended every three days
Read 15 Oct 2026 · letsencrypt.org
On the record
- ACME clients
- Users must operate an ACME client; the documentation recommends Certbot for most people and lists many alternatives.letsencrypt.org · read 15 Oct 2026
- API
- The production ACME directory endpoint is https://acme-v02.api.letsencrypt.org/directory and a separate staging endpoint is provided for testing.letsencrypt.org · read 15 Oct 2026
- Automation
- The ACME protocol verifies control of a domain and is used to issue certificates; clients can automate certificate management and renewal.letsencrypt.org · read 9 Oct 2026
- Certificate lifetime
- Default certificates are valid for 90 days; subscribers can opt in to certificates valid for six days, and these lifetimes cannot be adjusted.letsencrypt.org · read 9 Oct 2026
- Certificate transparency
- Issued certificates are submitted to public Certificate Transparency logs.letsencrypt.org · read 15 Oct 2026
- Certificate types
- The service issues standard Domain Validation certificates for domain-based servers, including web, mail and FTP servers.letsencrypt.org · read 15 Oct 2026
- Company founded
- LinkedIn lists Internet Security Research Group as founded in 2013.linkedin.com · read 15 Oct 2026
- Company size
- LinkedIn lists ISRG as having 11–50 employees.linkedin.com · read 15 Oct 2026
- Developer testing
- The Pebble project is a miniature ACME server intended for client testing, while Boulder is the production CA implementation.letsencrypt.org · read 15 Oct 2026
- Documentation
- The official documentation covers onboarding, ACME clients, rate limits, staging, certificate policy, challenge types, profiles, revocation, compatibility and integration guidance.letsencrypt.org · read 15 Oct 2026
- Domain validation
- Applicants prove domain control through challenges such as DNS records or HTTP resources.letsencrypt.org · read 15 Oct 2026
- HTTPS automation
- The ACME protocol lets an ACME client obtain browser-trusted HTTPS certificates without manual intervention.letsencrypt.org · read 15 Oct 2026
- Integrations
- Hosting providers can obtain and manage certificates for customers through their own ACME clients.letsencrypt.org · read 15 Oct 2026
- Intended users
- The service is available to people and organizations worldwide that need certificates for domain-named servers, including web, mail, and FTP servers.letsencrypt.org · read 9 Oct 2026
- Legal structure
- ISRG describes itself as a California public benefit corporation recognized as a tax-exempt 501(c)(3) organization.isrg.org · read 15 Oct 2026
- License
- Boulder is open source under the Mozilla Public License 2.0.github.com · read 15 Oct 2026
- Limit: abuse complaints
- Trustpilot includes one-star complaints alleging that certificates were issued to phishing or scam domains.trustpilot.com · read 15 Oct 2026
- Limit: issuance limits complaint
- A Trustpilot reviewer reported repeated exact-domain certificate rate-limit errors despite claiming no recent changes to the domain.trustpilot.com · read 15 Oct 2026
