Rust: What is the difference between Box and Rc?

Box — single ownership, heap. Rc — reference counting, multiple owners.

Box:

• Single owner.
• Heap allocation.
• Cannot be shared.

Rc:

• Multiple owners.
• Reference counting.
• Single-threaded only.

1let b = Box::new(5);
2// b cannot be shared
3
4use std::rc::Rc;
5let r1 = Rc::new(5);
6let r2 = Rc::clone(&r1);  // Shared

Key: Box for single ownership, Rc for shared ownership.