ENGINE code removed from the OpenSSL Library

[Blog on OpenSSL Library]

OpenSSL 4.0, to be released in April 2026, is the first [major
release](https://openssl-library.org/policies/releasestrat/index.html) since
3.0 which [replaced the ENGINE interface with _Providers_](https://openssl-
library.org/post/2019-02-13-fips-update/). Removing ENGINEs is a primary goal
of this major release and this post describes the change agreed to by both the
OpenSSL Corporation and OpenSSL Foundation.

## Summary

All symbols defined in `openssl/engine.h` have been removed from the [shared
library](https://en.wikipedia.org/wiki/Shared_library) in OpenSSL 4.0.
Applications that use the ENGINE API will fail to compile using the default
build settings. This behavior matches what happens in previous versions when
building OpenSSL with the [`no-engine` configuration
option](https://github.com/openssl/openssl/blob/master/INSTALL.md#no-engine)
with current versions. Up-to-date applications should not include
`openssl/engine.h` at all.



URL: https://openssl-library.org/post/2025-12-18-remove-engines/