---
title: "What are the differences between mutable and immutable borrowing in Rust?"  
description: "What are the differences between mutable and immutable borrowing in Rust?"  
author: "Steilla Mitchel"  
published: 2023-07-10  
updated: 2023-07-11  
canonical: https://www.mindstick.com/forum/159010/what-are-the-differences-between-mutable-and-immutable-borrowing-in-rust  
category: "rust"  
tags: ["string", "rust"]  
reading_time: 2 minutes  

---

# What are the differences between mutable and immutable borrowing in Rust?

What are the [differences](https://www.mindstick.com/articles/12918/cat-5e-vs-cat-6a-understanding-the-major-differences) between [mutable and immutable](https://www.mindstick.com/forum/161888/what-are-python-s-mutable-and-immutable-types) borrowing in [Rust](https://www.mindstick.com/forum/160170/explain-rust-s-ownership-borrowing-and-lifetimes-system)?

## Replies

### Reply by Aryan Kumar

Sure. In Rust, there are two types of borrowing: mutable and [immutable](https://www.mindstick.com/interview/2439/how-to-create-immutable-class). Mutable borrowing allows you to modify the value that is being borrowed, while immutable borrowing only allows you to read the value.

Here is an example of mutable borrowing in Rust:

Rust

```plaintext
let mut string = String::from("Hello, world!");

let mutable_borrow = &mut string;

mutable_borrow.push_str(", Rust!");
```

In this example, the variable `string` is mutable. This means that we can borrow the variable mutablely, using the `&mut` keyword. The mutable borrow allows us to modify the value of the variable, as shown by the `push_str()` method.

Here is an example of immutable borrowing in Rust:

Rust

```plaintext
let string = String::from("Hello, world!");

let immutable_borrow = &string;

println!("{}", immutable_borrow);
```

In this example, the variable `string` is immutable. This means that we can only borrow the variable immutably, using the `&` keyword. The immutable borrow only allows us to read the value of the variable, as shown by the `println!()` macro.

The main difference between mutable and immutable borrowing is that mutable borrowing allows you to modify the value that is being borrowed, while immutable borrowing only allows you to read the value.

Here is a table that summarizes the key differences between mutable and immutable borrowing in Rust:

| Feature | Mutable borrowing | Immutable borrowing |
| --- | --- | --- |
| Can modify the value? | Yes | No |
| Can be used with `&mut` | Yes | No |
| Can be used with `&` | No | Yes |

Here are some of the benefits of using mutable and immutable borrowing in Rust:

- **Safety:** Rust's borrowing system prevents data races by ensuring that only one mutable borrow to a value can exist at a time.
- **Expressiveness:** Rust's borrowing system allows you to express complex ownership relationships in a concise way.
- **Performance:** Rust's borrowing system can improve the performance of code by avoiding unnecessary copies.

Overall, Rust's borrowing system is a powerful tool that can help you to write reliable, safe, and performant code.


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Original Source: https://www.mindstick.com/forum/159010/what-are-the-differences-between-mutable-and-immutable-borrowing-in-rust

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