Skip to content
Free public beta until December 4, 2026: every course is open, no card needed. After that, the first chapter of each course stays free and full access is a one-time $39 ($19 for up to 100 founding members chosen for helpful feedback). Your progress is kept. How the beta works

fat pointer

A pointer that carries a second word of information, like a length or a vtable.

A fat (wide) pointer is two words: a data pointer plus metadata, which is a length for slices and str and a vtable pointer for trait objects.

Loading interactive…

Examples

  • On a 64-bit machine size_of::<&Email>() is 8, while size_of::<&dyn Notifier>(), size_of::<Box<dyn Notifier>>() and size_of::<&str>() are each 16.

See also

vtable trait object slice
Read the full section →