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openssl / openssl

git clone https://github.com/openssl/openssl.git openssl-4.0.3 · 23d ago 🔥 on GitHub Trending today

General-purpose toolkit implementing TLS, DTLS, and QUIC protocols on top of a standalone cryptographic library and CLI.

Why you might care

OpenSSL is the long-standing reference TLS and crypto library, used as the basis for many systems and applications. It includes libssl, libcrypto usable independently, a FIPS-validated module, and a command-line tool for certificates, digests, and encryption.

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31k
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12k
forks · 1.6k open issues

Star history (as recorded here)

2026-10-20 · 30,995 ★ 2026-10-22 · 31,011 ★
LanguageC
LicenseApache-2.0
Created2013-01-15 (13y ago)
Last pushtoday
Watchers1.0k
OwnerOrganization

Seen on GitHub Trending

  • 2026-10-22 — #5 daily in c · +10 ★
  • 2026-10-22 — #18 monthly in c · +342 ★
  • 2026-10-21 — #15 monthly in c · +338 ★
  • 2026-10-20 — #15 monthly in c · +338 ★

GitHub topics

Links

README excerpt
Welcome to the OpenSSL Project
==============================
[![openssl logo]][www.openssl.org]
[![github actions ci badge]][github actions ci]
OpenSSL is a robust, commercial-grade, full-featured Open Source Toolkit
for the Transport Layer Security (TLS, formerly SSL), Datagram TLS (DTLS), and QUIC protocols.
The protocol implementations are based on a full-strength general purpose
cryptographic library, which can also be used stand-alone. Also included is a
cryptographic module validated to conform with FIPS standards.
OpenSSL is descended from the SSLeay library developed by Eric A. Young
and Tim J. Hudson.
The official Home Page of the OpenSSL Project is [www.openssl.org].
Table of Contents
=================
 - Overview
 - Download
 - Build and Install
 - Documentation
 - License
 - Support
 - Contributing
 - Legalities
Overview
========
The OpenSSL toolkit includes:
- **libssl**
 an implementation of all TLS protocol versions up to TLSv1.3 ([RFC 8446]),
 DTLS protocol versions up to DTLSv1.3 ([RFC 9147]) and
 the QUIC version 1 protocol ([RFC 9000]).
- **libcrypto**
 a full-strength general purpose cryptographic library. It constitutes the
 basis of the TLS implementation, but can also be used independently.
- **openssl**
 the OpenSSL command line tool, a Swiss Army knife for cryptographic tasks,
 testing and analyzing. It can be used for
 - creation of key parameters
 - creation of X.509 certificates, CSRs and CRLs
 - calculation of message digests
 - encryption and decryption
 - SSL/TLS/DTLS and client and server tests
 - QUIC client tests
 - handling of S/MIME signed or encrypted mail
 - and more...
Download
========
For Production Use
------------------
Source code tarballs of the official releases can be downloaded from
openssl-library.org/source/.
The OpenSSL project does not distribute the toolkit in binary form.
However, for a large variety of operating systems precompiled versions
of the OpenSSL toolkit are available. In particular, on Linux and other
Unix operating systems, it is normally recommended to link against the
precompiled shared libraries provided by the distributor or vendor.
We also maintain a list of third parties that produce OpenSSL binaries for
various Operating Systems (including Windows) on the [Binaries] page on our
wiki.
For Testing and Development
---------------------------
Although testing and development could in theory also be done using
the source tarballs, having a local copy of the git repository with
the entire project history gives you much more insight into the
code base.
The main OpenSSL Git repository is private.
There is a public GitHub mirror of it at [github.com/openssl/openssl],
which is updated automatically from the former on every commit.
A local copy of the Git repository can be obtained by cloning it from
the GitHub mirror using
 git clone https://github.com/openssl/openssl.git
If you intend to contribute to OpenSSL, either to fix bugs or contribute
new features, you need to fork the GitHu

Blurb generated by claude-haiku-5-5 1d ago. Star deltas marked ~ are extrapolated from partial history.