OPENSSL_INIT_SSL(3ossl)

💖 OPENSSL_INIT_SSL 💖

okay bestie, welcome to the OPENSSL_INIT_SSL(3ossl) page — yes it's the OpenSSL one, the libssl and libcrypto init situation, and honestly? it's giving "less work than you think". let's get into it 🫶

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✨ NAME ✨

OPENSSL_init_ssl — OpenSSL (libssl and libcrypto) initialisation

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✨ SYNOPSIS ✨

#include <openssl/ssl.h>

int OPENSSL_init_ssl(uint64_t opts, const OPENSSL_INIT_SETTINGS *settings);

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✨ DESCRIPTION ✨

so like. normally, when OpenSSL (that's libssl AND libcrypto, the whole duo 👯) does its normal-operation thing, it grabs a bunch of resources at start up, and those resources must be freed later when the library closes down. and that's not even the whole story — some resources are allocated on a per thread basis (only if your app is multi-threaded, no stress otherwise), and those ones have to be freed before the thread closes. periodt.

here's the slay part though: as of version 1.1.0, OpenSSL will automatically allocate all the resources it needs, so no explicit initialisation is required. like, none. and it also automatically deinitialises when it's supposed to. iconic behaviour, we love a self-sufficient library 💅

but — and there's always a but — sometimes you do want explicit initialisation, or straight up need it. for example when you want some nondefault initialisation. that's literally what OPENSSL_init_ssl() is for. calling it explicitly initialises BOTH libcrypto and libssl. if you only want to initialise ONLY libcrypto, go look at the OPENSSL_init_crypto(3) function instead, that's its whole thing.

now important: a lot of internal OpenSSL functions call OPENSSL_init_ssl() themselves. so if you're trying to do nondefault initialisation, your application code MUST call OPENSSL_init_ssl() before any other OpenSSL function calls. before. like, first. no cap. 🔥

the opts parameter is the one that says which aspects of libssl and libcrypto should get initialised. the valid options for libcrypto are all described over on the OPENSSL_init_crypto(3) page. and then, on top of any libcrypto-specific option, you also get these libssl options:

• OPENSSL_INIT_NO_LOAD_SSL_STRINGS — suppresses automatic loading of the libssl error strings. this one is not a default option. and heads up: once it's selected, any subsequent calls to OPENSSL_init_ssl() with the option OPENSSL_INIT_LOAD_SSL_STRINGS will just be ignored. 🙈
• OPENSSL_INIT_LOAD_SSL_STRINGS — automatic loading of the libssl error strings. this one is a default option. and once it's selected, subsequent calls to OPENSSL_init_ssl() with the option OPENSSL_INIT_LOAD_SSL_STRINGS will be ignored.

OPENSSL_init_ssl() also takes a settings parameter, which you can use to set parameter values. all the details on that live in OPENSSL_init_crypto(3) 💜

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✨ RETURN VALUES ✨

OPENSSL_init_ssl() returns 1 on success or 0 on error. that's it, that's the whole vibe check.

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✨ SEE ALSO ✨

• OPENSSL_init_crypto(3)

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✨ HISTORY ✨

the OPENSSL_init_ssl() function was added in OpenSSL 1.1.0. so it's been here a minute 🎀

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✨ COPYRIGHT ✨

Copyright 2016-2020 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

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and that's the whole page bestie, mwah 💋 this little number is from OpenSSL version 3.5.9, dated 2026-09-29, and yes it's the OPENSSL_INIT_SSL(3ossl) manual — go init something, you've got this ⭐🧚‍♀️