What is Lego used for?

Lego is an ACME client and Go library for obtaining and renewing TLS certificates from Let's Encrypt and other certificate authorities. It is a good fit for automating Let's Encrypt renewals and embedding certificate management in Go apps.

Yes. Lego is open source under the MIT licence. Its source code is on GitHub at go-acme/lego and is written mainly in Go.

Yes. Lego is open source, so the software itself is free to use.

What is Lego an alternative to?

Lego is an open-source alternative to DigiCert, Sectigo and GlobalSign. Other open-source alternatives to DigiCert include Certbot, acme.sh and step-ca.

Is Lego actively maintained?

Yes. The most recent commit to Lego was on 27 September 2026, and the latest release is v5.5.2, published on 23 September 2026. The project has 9.9k stars on GitHub.

Lego: open-source alternative to DigiCert, Sectigo

About Lego

Lego is an ACME client and library written in Go, built to obtain and renew certificates from Let's Encrypt and other ACME certificate authorities. It can be used as a command-line tool or embedded in other Go software, which makes HTTPS certificates easy to automate.

It implements ACME v2 as defined in RFC 8555 and supports related standards, including the TLS-ALPN challenge extension, certificates for IP addresses, Renewal Information and several draft extensions. Its challenge support covers HTTP-01, DNS-01 and TLS-ALPN-01, and it ships with integrations for more than 200 DNS providers. It can register with a CA, obtain certificates from scratch or from an existing CSR, renew and revoke them, and handle SAN certificates and custom challenge solvers.

Lego is released under the MIT license. It is described as an independent, free project that relies on donations, and its documentation is hosted online. If a DNS provider is missing, users are encouraged to open an issue to request support.

Key features

ACME v2 client per RFC 8555
HTTP-01, DNS-01 and TLS-ALPN-01 challenges
More than 200 DNS provider integrations
Obtain, renew and revoke certificates
SAN certificates and custom solvers
Usable as a CLI or Go library

Good fit for

→Automating Let's Encrypt renewals
→Embedding certificate management in Go apps

Built with: Go
Tags: acme; letsencrypt; tls; certificates; dns; https; go; cli

Lego: questions and answers

What is Lego used for?: Lego is an ACME client and Go library for obtaining and renewing TLS certificates from Let's Encrypt and other certificate authorities. It is a good fit for automating Let's Encrypt renewals and embedding certificate management in Go apps.
Is Lego open source?: Yes. Lego is open source under the MIT licence. Its source code is on GitHub at go-acme/lego and is written mainly in Go.
Is Lego free?: Yes. Lego is open source, so the software itself is free to use.
What is Lego an alternative to?: Lego is an open-source alternative to DigiCert, Sectigo and GlobalSign. Other open-source alternatives to DigiCert include Certbot, acme.sh and step-ca.
Is Lego actively maintained?: Yes. The most recent commit to Lego was on 27 September 2026, and the latest release is v5.5.2, published on 23 September 2026. The project has 9.9k stars on GitHub.