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Leo Programming Language

Leo is an imperative, statically typed programming language and command-line tool for developing private applications with zero-knowledge circuits for the Aleo ecosystem. It abstracts lower-level cryptographic concepts, compiles programs into circuits and Aleo instructions, and provides tools for unit testing, integration testing and console-based circuit checks.

Explore the practical guide ↓

Independent OpenViST project profile, based on linked sources.

Leo Programming Language — OpenViST project profile in Developer Tools.
OpenViST project illustration. See the linked sources for product details.
Understand the project

Practical overview

When it fits

Use Leo when the project requires a higher-level programming interface for private Aleo applications and a documented command-line workflow for compiling, checking and running zero-knowledge programs.

Who it is for

  • Developers building private applications for Aleo.
  • Engineers working with zero-knowledge circuits and Aleo instructions.
  • Teams that want a CLI-based workflow for compiling and testing circuit logic.

Documented uses

  • Write private application logic in a higher-level language.
  • Compile Leo programs into circuits and Aleo instructions.
  • Create unit and integration tests for circuit behavior.
  • Run documented build, setup, proving, verification and execution workflows from the CLI.
Before you choose

Requirements & limits

The repository documents installation through Rust and Cargo, or building from source. It provides guidance for Windows, Linux and macOS terminal environments. No account or pricing requirement is documented in the supplied material.

  • Aleo alignment matters because Leo is described as one part of the Aleo ecosystem.
  • Rust and Cargo are prerequisites for the documented installation routes.
  • The CLI covers compilation, proving, verification and execution in the quick-start workflow.
  • The project is identified as alpha software, so breaking changes are a documented consideration.
  • The GPL-3.0 license is relevant when evaluating how the tool fits into a development stack.

Check current requirements in the official documentation. Source-based guidance does not mean OpenViST has run or independently tested this project.

Source-based practical guide

Create and run a first Leo project

Use the documented Leo CLI quick-start flow to create a project and run its example program.

Before you start

  • Rust installed through the documented rustup process.
  • Leo installed with Cargo using the documented package names.
  • A terminal environment on Windows, Linux or macOS.

Steps

  1. Install Rust with rustup.

  2. Install Leo and its documented plugins with Cargo.

  3. Create a project with leo new helloworld.

  4. Enter the project directory and run leo run main 0u32 1u32.

Expected outcome

The Leo CLI compiles the program into Aleo instructions and runs it through the documented build, setup, prove and verify flow.

Guide limitations

  • The project describes Leo as alpha software subject to breaking changes.
  • This quick-start flow documents running a program, not production deployment.
Documentation 1 ↗
Evidence and transparency

Sources & review

Official repository ↗
Source record details
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Sources checked
3 October 2026
Original website title
ProvableHQ/leo · Official homepage title · retained in its source language
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