What Is Let's Encrypt and How Does Free SSL Work?

What is Let's Encrypt is a question almost everyone bringing a website to HTTPS runs into sooner or later. In short, Let's Encrypt is the world's most widely used free certificate authority, issuing SSL/TLS certificates for millions of domains every single day. In this article we explain step by step what Let's Encrypt is, how free SSL works, and why the whole process is so heavily automated.

What is Let's Encrypt

Let's Encrypt is a free, automated and open certificate authority (CA) operated by the non-profit ISRG (Internet Security Research Group). It has a single mission: to encrypt the entire web with HTTPS. Certificates are free because ISRG funds the project through sponsors and donations, paying for the infrastructure collectively instead of charging per certificate.

Let's Encrypt issues only DV (Domain Validation) certificates. That means the certificate proves you control the domain; it does not verify your company identity or legal entity. For the vast majority of blogs, corporate sites and online stores, that is more than enough.

How it works (ACME + validation)

The magic lives in the ACME (Automatic Certificate Management Environment) protocol. ACME is an open standard that fully automates requesting, validating and delivering certificates. It talks between a client and the Let's Encrypt servers without any human in the loop.

Before a certificate is issued, you must prove you actually control the domain. There are two main validation methods:

  • HTTP-01: Let's Encrypt gives you a token, which you place as a file under a specific path on your server (/.well-known/acme-challenge/). Let's Encrypt reads that file over HTTP to confirm the domain is under your control.
  • DNS-01: You add a value you are given as a TXT record in your DNS zone. Let's Encrypt queries that record to validate. This method is required when you cannot place a file on the server and for wildcard certificates.

Once validation succeeds, Let's Encrypt signs and delivers the certificate. A typical ACME flow looks like this:

1. Create account / generate key
2. Submit certificate order
3. Validate: HTTP-01 file or DNS-01 TXT record
4. Let's Encrypt verifies
5. Certificate signed and downloaded

For anyone who would rather not do this by hand, our free SSL wizard completes the process in minutes; you simply enter your domain and confirm the validation.

Why 90 days

Let's Encrypt certificates are valid for only 90 days. That may sound short, but it is a deliberate security choice:

  1. It encourages automation: A short lifetime makes manual renewal impractical and pushes everyone toward automation. An automatically renewed certificate is far safer than one that quietly expires because someone forgot.
  2. It limits the impact of a leaked key: If your private key is ever compromised, the damage lasts at most 90 days. With yearly certificates that window of risk is much wider.
Short-lived certificates are not a weakness for the health of the internet; on the contrary, they are a cornerstone of modern security.

Is it trustworthy

Yes. Let's Encrypt certificates are trusted by all major browsers (Chrome, Firefox, Safari, Edge) and operating systems. This is because Let's Encrypt's root certificates are included in those platforms' trust stores. They offer the same encryption strength (generally the same TLS standards) as a paid certificate, and the padlock in the address bar looks exactly the same.

Its limits (DV, wildcard, no OV/EV)

Let's Encrypt is powerful, but it does not do everything. Knowing its limits matters:

  • It issues only DV certificates; it does not offer OV or EV (organization/extended validation). If you need a company name shown in the browser, you must turn to a commercial CA.
  • Wildcard certificates (*.example.com) can be obtained only with DNS-01 validation; HTTP-01 does not work for wildcards.
  • It includes no commercial extras such as insurance, warranties or a green address bar.

Summary

Let's Encrypt is a free DV certificate authority operated by ISRG and fully automated through the ACME protocol. It validates domain ownership via HTTP-01 and DNS-01, boosts security with short-lived 90-day certificates, and is trusted by every major browser. Its only downside is that command-line tools can feel complex for beginners. That is exactly where our free SSL wizard comes in: no membership required, you enter your domain, complete the validation, and download your CRT, KEY, CA Bundle, fullchain and PFX files in a single ZIP. Use the full power of Let's Encrypt in minutes, with no technical knowledge required.