Certbot is part of EFF’s effort to encrypt the entire Internet. Secure communication over the Web relies on HTTPS, which requires the use of a digital certificate that lets browsers verify the identify of web servers (e.g., is that really google.com?). Web servers obtain their certificates from trusted third parties called certificate authorities (CAs). Certbot is an easy-to-use client that fetches a certificate from Let’s Encrypt—an open certificate authority launched by the EFF, Mozilla, and others—and deploys it to a web server.
Anyone who has gone through the trouble of setting up a secure website knows what a hassle getting and maintaining a certificate is. Certbot and Let’s Encrypt can automate away the pain and let you turn on and manage HTTPS with simple commands. Using Certbot and Let's Encrypt is free, so there’s no need to arrange payment.
How you use Certbot depends on the configuration of your web server. The best way to get started is to use our interactive guide. It generates instructions based on your configuration settings. In most cases, you’ll need root or administrator access to your web server to run Certbot.
If you’re using a hosted service and don’t have direct access to your web server, you might not be able to use Certbot. Check with your hosting provider for documentation about uploading certificates or using certificates issues by Let’s Encrypt.
Certbot is a fully-featured, extensible client for the Let's Encrypt CA (or any other CA that speaks the ACME protocol) that can automate the tasks of obtaining certificates and configuring webservers to use them. This client runs on Unix-based operating systems.
Until May 2016, Certbot was named simply
letsencrypt-auto, depending on install method. Instructions on the Internet, and some pieces of the software, may still refer to this older name.
If you'd like to contribute to this project please read Developer Guide.
The easiest way to install Certbot is by visiting certbot.eff.org, where you can find the correct installation instructions for many web server and OS combinations. For more information, see Get Certbot.
How to run the client
In many cases, you can just run
certbot, and the client will guide you through the process of obtaining and installing certs interactively.
For full command line help, you can type:
./certbot-auto --help all
You can also tell it exactly what you want it to do from the command line. For instance, if you want to obtain a cert for
other.example.net, using the Apache plugin to both obtain and install the certs, you could do this:
./certbot-auto --apache -d example.com -d www.example.com -d other.example.net
(The first time you run the command, it will make an account, and ask for an email and agreement to the Let's Encrypt Subscriber Agreement; you can automate those with
If you want to use a webserver that doesn't have full plugin support yet, you can still use "standalone" or "webroot" plugins to obtain a certificate:
./certbot-auto certonly --standalone --email email@example.com -d example.com -d www.example.com -d other.example.net
Understanding the client in more depth
To understand what the client is doing in detail, it's important to understand the way it uses plugins. Please see the explanation of plugins in the User Guide.
Software project: https://github.com/certbot/certbot
Notes for developers: https://certbot.eff.org/docs/contributing.html
Main Website: https://certbot.eff.org
Let's Encrypt Website: https://letsencrypt.org
ACME spec: http://ietf-wg-acme.github.io/acme/
ACME working area in github: https://github.com/ietf-wg-acme/acme
The Let's Encrypt Client presently only runs on Unix-ish OSes that include Python 2.6 or 2.7; Python 3.x support will hopefully be added in the future. The client requires root access in order to write to
/var/lib/letsencrypt; to bind to ports 80 and 443 (if you use the
standalone plugin) and to read and modify webserver configurations (if you use the
nginx plugins). If none of these apply to you, it is theoretically possible to run without root privileges, but for most users who want to avoid running an ACME client as root, either letsencrypt-nosudo or simp_le are more appropriate choices.
The Apache plugin currently requires a Debian-based OS with augeas version 1.0; this includes Ubuntu 12.04+ and Debian 7+.
- Supports multiple web servers:
- apache/2.x (beta support for auto-configuration)
- nginx/0.8.48+ (alpha support for auto-configuration)
- webroot (adds files to webroot directories in order to prove control of domains and obtain certs)
- standalone (runs its own simple webserver to prove you control a domain)
- other server software via third party plugins
- The private key is generated locally on your system.
- Can talk to the Let's Encrypt CA or optionally to other ACME compliant services.
- Can get domain-validated (DV) certificates.
- Can revoke certificates.
- Adjustable RSA key bit-length (2048 (default), 4096, ...).
- Can optionally install a http -> https redirect, so your site effectively runs https only (Apache only)
- Fully automated.
- Configuration changes are logged and can be reverted.
- Supports ncurses and text (-t) UI, or can be driven entirely from the command line.
- Free and Open Source Software, made with Python.
For extensive documentation on using and contributing to Certbot, go to https://certbot.eff.org/docs. If you would like to contribute to the project or run the latest code from git, you should read our developer guide.