Stack vs Heap Memory in Rust

Updated

October 31, 2026

Stack vs Heap Memory in Rust

Understanding where data lives is essential for writing efficient Rust code.

The Stack

  • Fast, LIFO (Last In, First Out) allocation.
  • All data stored on the stack must have a known, fixed size at compile time.
  • Primitive types, fixed arrays, and function frames live on the stack.

The Heap

  • Dynamic memory allocated at runtime.
  • The operating system locates a contiguous region of memory, marks it in use, and returns a pointer.
  • Slower than stack allocation; requires dereferencing pointers.
  • Dynamically sized types like String and Vec<T> store metadata on the stack (pointer, length, capacity) pointing to heap buffers.