Cargo Features

fernet = { version = "0.2.1", default-features = false, features = ["fernet_danger_timestamps", "rustcrypto", "openssl"] }
default = openssl

The openssl feature is set by default whenever fernet is added without default-features = false somewhere in the dependency tree.

rustcrypto = aes, cbc, hmac, sha2, subtle

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features.

openssl default
aes rustcrypto?
cbc rustcrypto?

With alloc and default (block-padding)

hmac rustcrypto?
sha2 rustcrypto?

With default (std)

subtle rustcrypto?

With default features