What Is Let's Encrypt and What Does It Do?
Let's Encrypt is a free, automated, and open Certificate Authority (CA) that issues TLS certificates so websites can enable HTTPS encryption. It is operated by the Internet Security Research Group (ISRG), a nonprofit organization, and according to its website it provides free TLS certificates to more than 700 million websites. If you own or manage a domain and want HTTPS without paying for certificates or configuring them by hand, Let's Encrypt is built for that use case.
What Let's Encrypt actually provides
A TLS certificate is what lets a browser establish an encrypted connection to your site and verify that it is talking to the domain it claims to be. Let's Encrypt issues those certificates at no cost and designs the process to be automated rather than manual.
The three words in its own description matter:
- Free — no payment is required to obtain a certificate.
- Automated — issuance and renewal are meant to run through software (ACME clients), not by hand.
- Open — the CA and its processes are open, and it is run by a nonprofit rather than a commercial vendor.
Who runs it
Let's Encrypt is a project of the Internet Security Research Group (ISRG), described on the site as a 501(c)(3) public benefit organization focused on making the Internet more secure and private. Funding comes from donations and corporate sponsorship, which is how the certificates stay free.
ISRG also operates two sibling projects alongside Let's Encrypt, all under the same nonprofit umbrella.
How you get a certificate
The key requirement is stated plainly on the site: to get a certificate for your website's domain, you have to demonstrate control over that domain. That domain-validation step is what prevents someone from obtaining a certificate for a domain they don't own.
The practical path looks like this:
- Choose an ACME client. Let's Encrypt maintains a list of recommended ACME clients that automatically manage your certificates. The client is the software that talks to Let's Encrypt on your behalf.
- Prove control of your domain. The client handles the challenge that demonstrates you control the domain.
- Receive and install the certificate. The client obtains the certificate and configures it for your server.
- Renew automatically. Because certificates expire, the client is designed to renew them without manual intervention — this is the main reason automation matters.
If you'd rather understand the process before running it, Let's Encrypt publishes documentation covering its certificate issuance process and best practices.
When Let's Encrypt is the right fit
| Situation | Let's Encrypt fits? |
|---|---|
| You want HTTPS on a site you control and want to avoid certificate costs | Yes — free certificates are the core offering |
| You can run or install an ACME client on your server | Yes — automation is the intended workflow |
| You need to prove domain control as part of issuance | Yes — this is a required step, not optional |
| You want technical help from other users | Yes — there is a community forum with experts, volunteers, and ISRG staff |
Where to go next
- Getting started: the site's "Get Started" path walks through securing a site with a free certificate.
- Documentation: read up on the issuance process and best practices before deploying.
- ACME clients: browse the recommended clients to pick one that matches your server setup.
- Community forum: ask questions and share knowledge with other users and ISRG staff.
The short version: if you control a domain and can automate certificate management, Let's Encrypt gives you free TLS certificates through a nonprofit CA — and its scale (700M+ websites) reflects how widely that model has been adopted.