> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/provablehq/leo/llms.txt
> Use this file to discover all available pages before exploring further.

# Introduction to Leo

> Learn about Leo, the imperative, statically-typed programming language for writing private applications on Aleo

# Introduction to Leo

Welcome to Leo, the programming language designed for building private applications on the Aleo blockchain.

## What is Leo?

Leo is an imperative, statically-typed programming language that abstracts low-level cryptographic concepts and makes it easy to integrate private applications into your stack. Leo compiles to circuits, making zero-knowledge proofs practical.

<Info>
  Leo provides a high-level language that makes zero-knowledge proofs accessible to developers without requiring deep cryptographic knowledge.
</Info>

## Key Features

**Developer-Friendly Syntax**

The syntax of Leo is influenced by traditional programming languages like JavaScript, Scala, and Rust, with a strong emphasis on readability and ease-of-use.

**Built for Privacy**

Leo compiles directly to Aleo instructions, enabling you to build applications with built-in privacy guarantees on the Aleo blockchain.

**Comprehensive Testing Tools**

Leo offers developers tools to sanity check circuits including:

* Unit tests
* Integration tests
* Console functions for debugging

**Type Safety**

As a statically-typed language, Leo catches errors at compile time, providing a safer development experience.

## The Aleo Ecosystem

Leo is one part of a greater ecosystem for building private applications on [Aleo](https://aleo.org/). The language works seamlessly with:

* **Aleo blockchain** - The underlying Layer 1 blockchain that executes Leo programs
* **snarkVM** - The virtual machine that runs Aleo instructions
* **snarkOS** - The decentralized operating system for the Aleo network

## Example Leo Program

Here's a simple Leo program that adds two numbers:

```leo theme={null}
program helloworld.aleo {
    // The 'helloworld' main function.
    fn main(public a: u32, b: u32) -> u32 {
        return a + b;
    }
}
```

<Note>
  Leo is currently in active development and the language is subject to updates and improvements. Check the [GitHub repository](https://github.com/ProvableHQ/leo) for the latest changes.
</Note>

## Use Cases

Leo is ideal for building:

* **Private DeFi applications** - Create tokens, DEXs, and financial instruments with privacy guarantees
* **Private voting systems** - Build governance mechanisms where votes remain confidential
* **Confidential gaming** - Develop games with hidden state and fair outcomes
* **Private identity solutions** - Create identity systems that preserve user privacy

## Version Information

The current version of Leo is **3.4.0**. Leo requires Rust **1.93.1** or later.

## Next Steps

<CardGroup cols={2}>
  <Card title="Install Leo" icon="download" href="/installation">
    Get Leo installed on your system
  </Card>

  <Card title="Quick Start" icon="rocket" href="/quickstart">
    Build your first Leo program
  </Card>
</CardGroup>

## License

Leo is open source software licensed under [GNU General Public License v3.0](https://github.com/ProvableHQ/leo/blob/master/LICENSE.md).