In short: getting and installing SSL/TLS certificates made easy (watch demo video).

The Let's Encrypt Client is a tool to automatically receive and install X.509 certificates to enable TLS on servers. The client will interoperate with the Let's Encrypt CA which will be issuing browser-trusted certificates for free beginning the summer of 2015.

It's all automated:

• The tool will prove domain control to the CA and submit a CSR (Certificate Signing Request).
• If domain control has been proven, a certificate will get issued and the tool will automatically install it.

All you need to do is:

user@www:~$ sudo letsencrypt -d www.example.org auth

and if you have a compatible web server (Apache or Nginx), Let's Encrypt can not only get a new certificate, but also deploy it and configure your server automatically!:

user@www:~$ sudo letsencrypt -d www.example.org run

Encrypt ALL the things!

This is a DEVELOPER PREVIEW intended for developers and testers only.

DO NOT RUN THIS CODE ON A PRODUCTION SERVER. IT WILL INSTALL CERTIFICATES SIGNED BY A TEST CA, AND WILL CAUSE CERT WARNINGS FOR USERS.

• web servers supported:
  • apache/2.x (tested and working on Ubuntu Linux)
  • nginx/0.8.48+ (tested and mostly working on Ubuntu Linux)
  • standalone (runs its own webserver to prove you control the domain)
• the private key is generated locally on your system
• can talk to the Let's Encrypt (demo) CA or optionally to other ACME compliant services
• can get domain-validated (DV) certificates
• can revoke certificates
• adjustable RSA key bitlength (2048 (default), 4096, ...)
• optionally can install a http->https redirect, so your site effectively runs https only (Apache only)
• fully automated
• configuration changes are logged and can be reverted using the CLI
• text and ncurses UI
• Free and Open Source Software, made with Python.

Documentation: https://letsencrypt.readthedocs.org/

Software project: https://github.com/letsencrypt/lets-encrypt-preview

Notes for developers: CONTRIBUTING.md

Main Website: https://letsencrypt.org/

IRC Channel: #letsencrypt on Freenode

Mailing list: client-dev (to subscribe without a Google account, send an email to client-dev+subscribe@letsencrypt.org)