---
title: "LEAN Engine Versions"
description: "The latest master branch on the LEAN repository is the engine branch that runs the backtesting, research, and live trading nodes in QuantConnect Cloud."
canonical: https://www.quantconnect.com/docs/v2/local-platform/development-environment/lean-engine-versions
markdown: https://www.quantconnect.com/docs/v2/local-platform/development-environment/lean-engine-versions.md
language: python
source: https://github.com/QuantConnect/Documentation/tree/master/02%20Local%20Platform/04%20Development%20Environment/08%20LEAN%20Engine%20Versions
modified: 2026-10-29
index: https://www.quantconnect.com/llms.txt
---

# LEAN Engine Versions

[Documentation](https://www.quantconnect.com/docs/v2.md) > [Local Platform](https://www.quantconnect.com/docs/v2/local-platform.md) > Development Environment > LEAN Engine Versions

> Code examples are shown in Python. Append `?lang=csharp` to this URL for the C# version of this page.

## Introduction

The latest master branch on the LEAN GitHub repository is the default engine branch that runs backtests, research notebooks, and live trading algorithms. The latest version of LEAN is generally the safest as it includes all bug fixes.

## Change Branches

Follow these steps to change the LEAN engine branch that runs your backtests and live trading algorithms:

1. [Open a project](https://www.quantconnect.com/docs/v2/local-platform/projects/getting-started.md#04-Open-Projects).
2. In the left navigation menu, click the ![](https://cdn.quantconnect.com/i/tu/vscode-qc-icon.jpg)**QuantConnect** icon.
3. In the Project panel, click the **LEAN Engine** field and then click a branch from the drop-down menu.
4. (Optional) Click **About Version** to display the branch description.
5. If you want to always use the master branch, select the **Always use Master Branch** check box.
6. Click **Select**.

Changing the Lean engine branch only affects the current project. If you [create a new project](https://www.quantconnect.com/docs/v2/local-platform/projects/getting-started.md#03-Create-Projects), the new project will use the master branch by default.

## Custom Branches

To create and use custom versions of LEAN, see [Custom Docker Images](https://www.quantconnect.com/docs/v2/lean-cli/projects/custom-docker-images.md).