How to Use pub to Control Visibility in Rust

Use the pub keyword before an item to make it accessible outside its current module. By default, items in Rust are private, so adding pub explicitly exposes functions, structs, or modules to the rest of the crate or external crates.

pub fn public_function() {
    println!("This is visible everywhere");
}

struct PrivateStruct {
    value: i32,
}

pub struct PublicStruct {
    pub value: i32,
}

The pub keyword can also be applied to struct fields individually to control granular visibility.

The pub keyword acts like a public sign on a door, allowing anyone to enter and use what's inside. Without it, your code is private and only accessible within the same file or module. You use it whenever you want other parts of your program or other libraries to call your functions or access your data.