BepInEx
github.com
What it is
BepInEx is a plugin and modding framework for Unity Mono and IL2CPP games, as well as .NET Framework games such as those built with XNA, FNA, and MonoGame. It provides configuration and logging, runtime method patching, and in-memory assembly patching. Runtime patching uses Harmony, including HarmonyX and MonoMod; in-memory patching uses Mono.Cecil with UnityDoorstop. The installation guide lists Windows, Linux, and macOS, though supported operating system versions and architectures depend on the build and game. Setup is manual: download the appropriate build and put its contents in the game’s root folder. Official binaries are available as stable and bleeding edge builds; the documentation recommends stable in most cases and notes that bleeding edge builds tend to be buggier. The project is open source under LGPL-2.1 and links to guides for users and developers. Compatibility has limits: stable releases are available only for Unity Mono, BepInEx 6 documentation remains a work in progress, and BepInEx 5 plugins do not yet work with the 6.0.0 pre-release.
Spec sheet
- What it does
- BepInEx is a plugin and modding framework for Unity Mono, Unity IL2CPP and .NET Framework games, including XNA, FNA and MonoGame.Read 15 Oct 2026 · github.com
- Purpose
- BepInEx is a plugin and modding framework for Unity Mono, Unity IL2CPP, and .NET Framework games, including XNA, FNA, and MonoGame.Read 30 Sep 2026 · github.com
- Audience
- The docs provide instructions for installing BepInEx and writing plugins, indicating it is intended for people modding games and developing game plugins.Read 30 Sep 2026 · docs.bepinex.dev
- Security
- The GitHub repository's Security and quality page displays zero advisories.Read 30 Sep 2026 · github.com
- License
- The project is open source under the LGPL-2.1 license.Read 30 Sep 2026 · github.com
- Antivirus complaint
- A 2021 GitHub issue reports Norton deleting BepInEx.Preloader.dll as a threat, which the reporter associated with the loader's injection behavior.Read 15 Oct 2026 · github.com
- Antivirus false positive
- A GitHub discussion records Gridinsoft flagging winhttp.dll and .doorstop_version in the 5.4.23.2 archive, with the reporter concluding it appeared benign after checking a related issue.Read 15 Oct 2026 · github.com
- API documentation
- The API reference documents namespaces for core plugin classes, configuration, paths, bootstrap access and logging.Read 15 Oct 2026 · docs.bepinex.dev
- Assembly patching
- Mono.Cecil and UnityDoorstop enable in-memory patching of game assemblies.Read 15 Oct 2026 · docs.bepinex.dev
- BepInEx 6 limitation
- The BepInEx 6.0.0-pre.2 release warns that BepInEx 5 plugins do not yet work with it and that the prerelease has many issues.Read 15 Oct 2026 · github.com
- Bleeding-edge builds
- The builds site publishes platform-specific archives for Windows, Linux and macOS Unity Mono and IL2CPP, plus .NET Framework and CoreCLR targets.Read 15 Oct 2026 · builds.bepinex.dev
- Build channels
- Official binaries are available as stable builds and bleeding edge builds; the docs say stable builds are recommended in most cases and bleeding edge builds tend to be buggier.Read 30 Sep 2026 · docs.bepinex.dev
- Compatibility limit
- The repository says only Unity Mono has stable releases, and BepInEx 6 documentation is marked as work in progress.Read 30 Sep 2026 · github.com
- Compatibility matrix
- The repository marks Unity Mono for Windows, macOS and Linux; Unity IL2CPP for Windows and Linux but not macOS; and .NET/XNA with Mono on macOS and Linux.Read 15 Oct 2026 · github.com
- Configuration
- BepInEx includes a built-in configuration system for the framework and plugins.Read 15 Oct 2026 · docs.bepinex.dev
- Developer tooling
- The developer guide covers C# project setup, starter templates, logging, configuration files, preloader patchers and runtime method patching.Read 15 Oct 2026 · docs.bepinex.dev
- Drop-in installation
- The documentation lists drop-in installation as a core capability.Read 15 Oct 2026 · docs.bepinex.dev
- Ecosystem dependence
- PC Gamer says most Valheim mods require BepInEx and recommends installing its BepInExPack before additional mods.Read 15 Oct 2026 · pcgamer.com
- Engine requirements
- Supported engines include Unity 3 or newer plus XNA, FNA, MonoGame and other .NET Framework engines.Read 15 Oct 2026 · docs.bepinex.dev
- Features
- It provides drop-in installation, built-in configuration and logging, runtime method patching, and in-memory assembly patching.Read 30 Sep 2026 · docs.bepinex.dev
- Game support
- The documentation lists Unity 3 or newer and .NET Framework games such as XNA, FNA, and MonoGame as supported game engines.Read 30 Sep 2026 · docs.bepinex.dev
- Independent listing status
- SourceForge hosts an exact mirror, states it is not affiliated with BepInEx, and shows 430 downloads in the reported week.Read 15 Oct 2026 · sourceforge.net
- Installation
- BepInEx is installed manually by downloading the correct build and placing its contents in the game's root folder.Read 30 Sep 2026 · docs.bepinex.dev
- Installation method
- The official guide says installation is currently manual and requires choosing binaries for the game's runtime.Read 15 Oct 2026 · docs.bepinex.dev
- Latest stable release
- GitHub lists BepInEx 5.4.23.5 as the latest stable release and records fixes for Unity 2022.3.62f3, Doorstop 4.5.0 and Unity 6 logging.Read 15 Oct 2026 · github.com
- Licence
- The GitHub repository identifies the BepInEx project licence as LGPL-2.1.Read 15 Oct 2026 · github.com
- Limit: compatibility dependence
- Hysen Labs notes that plugin failures can follow game updates, runtime changes or obfuscation when targeted methods no longer exist.Read 15 Oct 2026 · hysenlabs.com
- Limit: documentation difficulty
- A Steam Deck Reddit thread reports that available guides were repetitive or incomplete and that following them still resulted in immediate game exits or no loaded mods.Read 15 Oct 2026 · reddit.com
- Limit: IL2CPP maturity
- Hysen Labs characterizes the IL2CPP path as less mature and notes that only Unity Mono has stable releases.Read 15 Oct 2026 · hysenlabs.com
- Limit: Steam Deck setup
- Reddit users report that Steam Deck installation can require different BepInEx versions, Proton settings and launch commands, with some installations failing to create plugin or configuration folders.Read 15 Oct 2026 · reddit.com
- Limit: version confusion
- Steam Deck users report that newer archives use different launch mechanisms from older releases and that downgrading to BepInEx 5.4.22.0 resolved problems for some setups.Read 15 Oct 2026 · reddit.com
- Loader compatibility
- Adapters are listed for BSIPA, IPA, MelonLoader, MonoMod, MuseDashModLoader, Partiality, Sybaris, UnityInjector, Unity Mod Manager and uMod.Read 15 Oct 2026 · github.com
- Logging
- BepInEx provides built-in logging for framework and plugin messages.Read 15 Oct 2026 · docs.bepinex.dev
- Maker identity
- The project presents itself as BepInEx, expanded as Bepis Injector Extensible, and credits contributors through its public GitHub repository.Read 15 Oct 2026 · github.com
- Operating systems
- The installation guide lists Windows, Linux, and macOS, with supported OS versions and architectures varying by build and game.Read 30 Sep 2026 · docs.bepinex.dev
- Operating-system requirements
- The guide lists Windows 7–10, Linux distributions with GCC 10 or newer, and macOS 10.13 or newer.Read 15 Oct 2026 · docs.bepinex.dev
- Patching integrations
- Runtime patching uses Harmony, including HarmonyX and MonoMod, while in-memory assembly patching uses Mono.Cecil with UnityDoorstop.Read 30 Sep 2026 · docs.bepinex.dev
- Plugin API
- Plugins are .NET DLLs placed in BepInEx/plugins and commonly inherit from BaseUnityPlugin with metadata attributes such as BepInPlugin and BepInDependency.Read 15 Oct 2026 · docs.bepinex.dev
- Praise: architecture
- Hysen Labs highlights the separation between the preloader, plugin-facing core and runtime-specific components as enabling early loading and extensibility.Read 15 Oct 2026 · hysenlabs.com
- Praise: feature breadth
- Softpedia describes BepInEx as free, open source and able to customize many features in Unity games.Read 15 Oct 2026 · softpedia.com
- Rating on Softpedia
- 4.5 out of 5 from 1 voteRead 15 Oct 2026 · softpedia.com
- Related loaders
- The repository lists loaders for BSIPA, IPA, MelonLoader, MonoMod, MuseDashModLoader, Partiality, Sybaris, UnityInjector, Unity Mod Manager, and uMod.Read 30 Sep 2026 · github.com
- Release status
- Release notes say BepInEx 5.4 is in long-term-support mode while main development moves to BepInEx 6.Read 15 Oct 2026 · github.com
- Runtime patching
- Harmony and MonoMod are used to support runtime method injection and patching.Read 15 Oct 2026 · docs.bepinex.dev
- Security concern
- Gridinsoft reports that antivirus alerts are more likely to be associated with repacked modpacks or unexplained extra files than with the official framework itself.Read 15 Oct 2026 · blog.gridinsoft.com
- Stable and preview channels
- Stable builds are hosted on GitHub, while bleeding-edge builds are published separately and are described as more experimental.Read 15 Oct 2026 · docs.bepinex.dev
- Support and guides
- The project links to user and developer guides and a Discord server, and its documentation covers installation, configuration, troubleshooting, and plugin development.Read 30 Sep 2026 · github.com
- Version limit
- The release notes state that BepInEx 5 is in long-term support and that BepInEx 5 plugins do not yet work with the BepInEx 6.0.0 pre-release.Read 30 Sep 2026 · github.com
Plans and prices
BepInEx Free open source · manual installation · stable and bleeding edge builds Read 30 Sep 2026 · github.com
BepInEx Free Free Stable releases · bleeding-edge builds · Unity Mono, IL2CPP and .NET/XNA framework game targets Read 15 Oct 2026 · github.com
Strong points and limits
Strong points
- Supports Unity and several .NET Framework game types.
- Includes configuration, logging, and patching tools.
- Stable and bleeding edge builds are available.
- Open source under the LGPL-2.1 license.
- User and developer guides are linked.
Limits
- Installation requires downloading and placing files manually.
- Stable releases cover Unity Mono only.
- BepInEx 6 documentation is work in progress.
- BepInEx 5 plugins do not yet work with 6.0.0 pre-release.
Who it suits
BepInEx suits people modding supported games or developing game plugins. Its documentation includes setup, configuration, troubleshooting, and plugin-development guides.
BepInEx in depth
Read the full write-up
BepInEx is a free mod-loading and plugin framework for Unity and.NET Framework games. It is best suited to players and developers working with compatible titles who need both a loader and built-in patching infrastructure. The trade-off is that manual installation and uneven version support make game and build matching essential.
Overview
BepInEx targets Unity Mono, Unity IL2CPP, and.NET Framework games, including XNA, FNA, and MonoGame projects. That makes it a broad foundation for game modification rather than a tool tied to one engine or a single title. Injection is the loading method, with plugin support, load-order control, and dependency handling included.
You download the appropriate build and put its files in the game’s root directory. For users comfortable managing game folders, this is a direct drop-in process; for everyone else, selecting the wrong build can prevent a successful start. Stable and bleeding-edge binaries are offered. Stable is the sensible default, while bleeding edge is for cases where newer support matters more than reliability and bugs are acceptable.
Key features
Built-in configuration and logging give plugins common settings and diagnostic facilities from the outset. That is useful for developers who want a shared base and for players troubleshooting a mod setup, although it does not remove the need to understand the target game’s compatibility requirements.
Runtime method patching is integrated through Harmony, including HarmonyX and MonoMod. In-memory assembly patching uses Mono.Cecil together with UnityDoorstop. These complementary approaches let plugin authors alter running behavior or patch assemblies in memory, making BepInEx suitable for substantial game changes rather than only simple content loading.
The project also lists loaders related to BSIPA, IPA, MelonLoader, MonoMod, MuseDashModLoader, Partiality, Sybaris, UnityInjector, Unity Mod Manager, and uMod. Guides cover installation, configuration, troubleshooting, and plugin development, with a Discord server for community support. It is open source under LGPL-2.1, and the repository’s security page displays zero advisories.
Pricing
PlanPriceWhat you getBepInExfreeOpen-source software, manual installation, and stable or bleeding-edge buildsThere are no paid tiers, trial period, seat charges, or usage quotas. The free plan is therefore the only fit for both individual players and plugin developers. Its cost advantage comes with a practical obligation: you handle installation and build selection yourself, rather than receiving a managed deployment.
Platforms
BepInEx supports Windows, macOS, and Linux. Supported operating-system versions and processor architectures vary by build and game, so platform compatibility cannot be judged from the operating-system label alone. The repository says stable releases are limited to Unity Mono; Unity IL2CPP and other targets may depend on less mature builds. BepInEx 6 documentation is work in progress, and BepInEx 5 remains in long-term support. Plugins made for BepInEx 5 do not yet work with the BepInEx 6.0.0 pre-release.
Who it's for
Choose BepInEx if you are modding a supported Unity or.NET Framework game, writing plugins, or need runtime and in-memory patching in one framework. Its configuration, logging, dependency handling, and load-order controls are particularly useful when a setup includes several plugins. It is a poor fit for anyone wanting a universal, one-click installer, or for a game whose required engine and release channel do not align with the available build.
Pros and cons
Pros
Supports Unity Mono, Unity IL2CPP, XNA, FNA, and MonoGame scenarios.
Combines injection-based loading with dependency and load-order controls.
Includes configuration, logging, Harmony-based runtime patching, and Mono.Cecil assembly patching.
Free and open source under LGPL-2.1, with guides for users and plugin developers.
Cons
Manual file placement makes compatibility and build selection the user’s responsibility.
Bleeding-edge builds are more bug-prone than the recommended stable channel.
Stable releases are limited to Unity Mono, while BepInEx 6 remains work in progress.
BepInEx 5 plugins are not compatible with the BepInEx 6.0.0 pre-release.
Alternatives
Game Mod Loaders is the broader comparison when you want to survey loaders across categories.
MelonLoader is another free option spanning Android, Linux, macOS, and Windows.
SMAPI is the free choice when your target is Stardew Valley 1.6.14 or later on its supported systems or Steam Deck.
Satisfactory Mod Loader is aimed at Satisfactory, with no required dependencies and Windows client/server plus Linux server support.
Everest is a free alternative supporting API, Linux, macOS, and Windows.
ModTek is a free BattleTech PC game mod loader.
MWSE is free software under GNU GPL for Linux and Windows.
Baldur's Gate 3 Script Extender is free to obtain under its published license, with the Commons Clause restricting resale of software whose value substantially derives from it.
Hollow Knight Modding API is free on Linux, macOS, and Windows with no paid tiers or usage limits stated.
Verdict
BepInEx is the right choice for technically confident mod users and plugin authors whose games match its supported engines and builds. Its strongest reason to choose it is the combination of broad game-framework coverage and serious patching tools at no cost. Look elsewhere when you need a managed installation experience, a stable non-Unity-Mono release, or immediate BepInEx 5 plugin compatibility on version 6.
Verdict
BepInEx combines game-plugin support with configuration, logging, and patching across several game frameworks. Check the build and game compatibility details first, especially if you need a non-Unity Mono stable release or BepInEx 5 plugin support on version 6.
Where Specifiction places it
- Game Mod Loaders#1 of 269.0
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