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ACME client

Project description

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 identity of web servers (e.g., is that really 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.

Certbot is meant to be run directly on your web server, not on your personal computer. 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 issued 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.

To see the changes made to Certbot between versions please refer to our changelog.


If you’d like to contribute to this project please read Developer Guide.

This project is governed by EFF’s Public Projects Code of Conduct.

How to run the client

The easiest way to install and run Certbot is by visiting, where you can find the correct instructions for many web server and OS combinations. For more information, see Get Certbot.

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.

System Requirements


Current Features

  • Supports multiple web servers:

    • apache/2.x

    • nginx/0.8.48+

    • webroot (adds files to webroot directories in order to prove control of domains and obtain certificates)

    • 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, …).

  • Adjustable EC key (secp256r1 (default), secp384r1, secp521r1).

  • 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 an interactive text 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 If you would like to contribute to the project or run the latest code from git, you should read our developer guide.

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