Cygwin and its libraries are continuously updated. Version numbers reflect OpenSSL releases, not the year. For example, cygcrypto-1.1.dll corresponds to OpenSSL 1.1.x series. The year 2021 has no specific meaning in this context.

The string “cygcrypto11dll 2021” appears in no official documentation, GitHub repository, or vendor release notes. Instead, it is a likely a fusion of:

Use ldd (from Cygwin itself) or a Windows tool like Dependency Walker to see exactly which DLLs are missing.

Users searching for this term in 2021 typically faced one of the following error messages on their Windows machines:

These errors often appeared when using popular developer tools ported from Linux, such as:

For nearly a decade, the standard version of OpenSSL was the 1.0.x series. Correspondingly, Cygwin users were accustomed to seeing cygcrypto-1.0.0.dll on their systems.

In late 2019 and throughout 2020 and 2021, the OpenSSL project officially ended support for the 1.0.x branch. This forced software maintainers and package managers (like the Cygwin setup program) to migrate to the newer 1.1.x branch.