# errorDescription A user-presentable description of the failure. ``` var errorDescription: String? { get } ``` ## Return Value A non-`nil` localized description for every case. ## Discussion Conforms to Foundation’s [`LocalizedError`](https://developer.apple.com/documentation/foundation/localizederror) contract: returns a short, human-readable string that begins with a noun phrase identifying the failure category (e.g. `"Invalid key: "`) and ends with the associated reason carried by the case. The returned string is the same value surfaced by `(error as NSError).localizedDescription` and by `String(describing:)` via `error.localizedDescription`. The value is deterministic for a given case-and-reason pair; it is not a cached property but recomputes each call. Callers that log or display the description should treat it as plain text suitable for end-user surfaces — it does not contain sensitive material such as key bytes or stack frames. > Note: The return type is `String?` to match the `LocalizedError` > protocol, but every case in ``doc://OpenSSL/documentation/OpenSSL/OpenSSLError`` produces a non-`nil` > value. Callers may safely unwrap with `??` against an empty > fallback.