Some parts of OTP has had limited VxWorks support, such as erl_interface. This support was removed in OTP 23. This limited support was formally deprecated as of OTP 22.

The old legacy erl_interface library (functions with prefix erl_) was removed in OTP 23. These parts of erl_interface has been informally deprecated for a very long time, and was formally deprecated in OTP 22. You typically want to replace the usage of the erl_interface library with the use of the ei library which also is part of the erl_interface application.

API functions in the module called httpd_conf was deprecated in favor of standard modules such as lists, string, filelib, and erlang. Formally deprecated as of OTP 18.

Support for the Apache-compatible config files was removed in OTP 23. A new config file format was introduced in OTP 12.

For security reasons SSL-3.0 is no longer supported at all.