Swift Academy · Lesson

The Sendable Protocol

Mark types safe to cross concurrency domains.

What Sendable Means

Sendable is a marker protocol. A type that conforms promises it is safe to share across concurrency domains without introducing data races.

It has no methods; it is a compiler-checked guarantee about thread safety.

protocol Sendable {}

Structs and enums whose stored properties are all Sendable can conform automatically.

Because values are copied when passed, each task gets its own independent copy.

struct User: Sendable {
    let id: Int
    let name: String
}