BepInEx

BepInEx is a free mod loader and plugin framework for Unity and .NET Framework games. It is best for players and developers whose games match its supported engines and builds. Its broad patching toolkit is useful, but manual setup and uneven release maturity make compatibility the deciding factor.

Overview

BepInEx supports Unity Mono and IL2CPP, as well as .NET Framework games built with XNA, FNA, or MonoGame. That makes it relevant across several game technologies, rather than to one named title. It serves players installing mods and developers writing plugins, with user and developer guides, troubleshooting help, and a Discord community.

Installation is manual: download the build suited to the game, then place its contents in the game’s root folder. This direct approach avoids a separate installer, but requires care when selecting a compatible build. Stable and bleeding-edge builds are available; stable builds are recommended for most cases, while bleeding-edge builds tend to be buggier.

Key features

The framework provides configuration and logging alongside plugin loading, giving developers shared tools instead of requiring each plugin to supply those basics. Runtime method patching is powered by Harmony integrations, including HarmonyX and MonoMod. For in-memory assembly patching, BepInEx uses Mono.Cecil with UnityDoorstop. These capabilities make it a flexible foundation for plugins that need to alter game behavior, though the specific game and framework version still determine whether it is a practical choice.

Mod loading uses injection, and the framework supports plugins, load-order control, and dependency handling. Those capabilities help organize a mod setup and its relationships, but do not remove the need to confirm compatibility with the target game.

Pricing

BepInEx is open-source software under the LGPL-2.1 license. Its BepInEx plan costs nothing and includes manual installation plus stable and bleeding-edge builds. There is no paid tier or trial to weigh against the free option; the meaningful trade-off is the time required to install it and select a suitable build.

Platforms

BepInEx supports Windows, macOS, and Linux. Supported operating-system versions and architectures vary by build and game, so platform availability alone does not guarantee a compatible setup. Check the game’s requirements and choose its matching build before installing.

Who it's for

BepInEx fits players looking to load mods in supported Unity or .NET Framework games, and developers building plugins for those games. Its configuration, logging, and patching tools are especially relevant to plugin authors. It is less suitable for anyone who needs a consistently stable release across all supported frameworks: stable releases are limited to Unity Mono, and BepInEx 6 documentation remains a work in progress.

Pros and cons

• Pros: Support for Unity Mono and IL2CPP as well as several .NET Framework game technologies gives modders and plugin authors a wider range of potential targets.
• Pros: Built-in configuration, logging, patching, load-order control, and dependency handling provide practical foundations for mod setups and plugin development.
• Pros: Free, open-source distribution avoids a purchase cost, while user and developer guides cover installation, troubleshooting, and plugin development.
• Cons: Manual placement in the game folder makes build selection and compatibility checks the user’s responsibility.
• Cons: Stable releases are limited to Unity Mono, and BepInEx 6 is still a work in progress; BepInEx 5 plugins do not yet work with the 6.0.0 pre-release.
• Cons: Bleeding-edge builds tend to be buggier, so they are a less dependable choice when stability matters.

Alternatives

Game Mod Loaders is the broader category to browse when you want to compare mod-loading options.

MelonLoader is another free option for Linux, macOS, Windows, and Android. SMAPI is free and is the relevant choice when modding Stardew Valley 1.6.14 or later on Linux, macOS, Windows, or Steam Deck.

ModTek is a free loader for BattleTech PC. MWSE is a free, GPL-licensed option for Linux and Windows that welcomes contributions such as bug fixes and documentation.

Satisfactory Mod Loader is free, has no required dependencies, and supports Windows clients and servers plus Linux servers. Cyber Engine Tweaks is a free, MIT-licensed framework for Linux and Windows.

Fallout 4 Script Extender (F4SE) is a free Windows option supporting Fallout 4 versions available on Steam and GOG. Hell2Modding is another free option for macOS and Windows.

Verdict

Choose BepInEx if you want a free, open-source loader and plugin toolkit for a compatible Unity or .NET Framework game, particularly if you value its patching and development facilities. Look elsewhere if your game lacks a suitable build or if you need stable support beyond Unity Mono; compatibility and release maturity are the limits that matter most.