# Introduction Welcome to **Customizing Builds With Release Profiles**. This lab is a part of the [Rust Book](https://doc.rust-lang.org/book/). You can practice your Rust skills in LabEx. In this lab, we will explore how to customize Rust's release profiles by adding `[profile.*]` sections to the `Cargo.toml` file and overriding default settings such as the `opt-level` for optimization.
Click the virtual machine below to start practicing