openMSX

openMSX is a free, open-source emulator for the MSX home computer system, with the project aiming for 100% accuracy. It emulates nearly all MSX, MSX2, MSX2+ and turboR systems, along with several others experimentally. The project lists more than 230 machine configurations and more than 110 extension hardware configurations. Its built-in graphical interface works across supported operating systems, and users can control the emulator with Tcl scripts or a command interface that also connects to external applications. A built-in debugger provides watchpoints, breakpoints, viewers and real-time data display. Save states and a reverse feature allow users to replay actions or step backward, with optional event-history recording. MIDI connectivity is available through host frameworks on Windows, Mac and Linux. Downloads include Windows, macOS, Linux, Android and source builds, though versions vary by platform. openMSX 20.0 and later requires OpenGL 2 support. Android support is listed only through version 0.15.0. The default C-BIOS machine lacks some functionality for a complete MSX setup.

openMSX combines broad MSX system emulation with scripting, debugging and reverse-playback tools. Check platform-specific versions and setup requirements, especially for Android and the default C-BIOS machine.

openMSX suits people looking to emulate MSX systems, including users who want scripting, debugging or save-and-rewind tools. Android users should note that listed support only extends through version 0.15.0.

openMSX is a free, open-source emulator for the MSX home computer family, aimed at players and developers who want detailed system coverage and tools beyond basic game playback. Its broad machine library, debugger and reverse-playback features make it a strong fit for technically curious MSX users, though setup and platform-specific limits matter.

Overview

openMSX aims for accurate emulation across almost all MSX, MSX2, MSX2+ and turboR systems, with some additional systems supported experimentally. A consistent built-in graphical interface works across supported operating systems. The breadth is a practical advantage for users moving among machine variants, while experimental support should not be treated as equivalent coverage.

The included library spans more than 230 machine configurations and over 110 extension hardware configurations. That range gives experienced users room to match different setups, but the default C-BIOS machine does not provide all the functionality of a complete MSX machine. Users seeking a fuller configuration should follow the setup guide and configure an actual MSX machine.

Key features

• Debugging: Watchpoints, breakpoints, viewers and real-time data display serve developers and users investigating how software behaves, not just those launching games.
• Control and scripting: Tcl scripts and a command interface over pipes or a UNIX domain socket allow external applications to control the emulator. This is useful for automation and custom workflows, though it adds a technical layer casual players may not need.
• Save and reverse playback: Save states and the ability to replay actions or step back through time make experimentation less costly. Optional event-history recording extends that capability.
• MIDI connectivity: On Windows, Mac and Linux, applications can connect to MIDI devices in the emulated MSX through host frameworks.

Catapult, the former separate GUI, is deprecated and no longer maintained. The project recommends the built-in interface in openMSX 20.0 and later, so users following older setup advice should account for that change.

Pricing

openMSX is free: the openMSX plan costs nothing and includes the MSX emulator, downloads and source code. There is no paid tier or trial to weigh against it. The trade-off is not a cheaper feature-limited plan but the setup and platform constraints of the software itself.

Platforms

Downloads include Windows, macOS, Linux x86 64-bit, Android ARM and source builds, though release versions differ by platform. openMSX 20.0 and later requires OpenGL 2 support. Android support is limited to version 0.15.0 and earlier, with Android 4.1+ support; readers on Android should not assume the newer desktop release applies to their device.

The download page offers Android, Linux, macOS and Windows builds. The software requires a BIOS. Shader/upscaling support is available.

Who it's for

openMSX suits MSX enthusiasts who need broad machine and extension coverage, and developers who value scripting, debugging, MIDI connectivity or reverse playback. It is less suitable for someone who wants a complete MSX configuration without setup, or who expects current openMSX releases on Android. Online manuals and documentation, Discord and IRC channels, an openMSX forum and a GitHub issue tracker provide routes for questions and bug reports.

Pros and cons

Pros

• Wide MSX coverage: More than 230 machine and 110 extension configurations support varied hardware setups.
• Tools for investigation: Debugging, Tcl control and reverse playback reach well beyond ordinary save-state emulation.
• Free and open-source: Downloads and source code are available without a paid plan.

Cons

• Setup is part of the experience: The default C-BIOS machine does not provide every function of a complete MSX machine.
• Android trails desktop releases: Android support is stated only through version 0.15.0.
• Graphics compatibility matters: Version 20.0 and later requires OpenGL 2 support.

Alternatives

For a broader multi-system directory, browse Multi-System Emulators. Consider these free alternatives when their platform or scope better fits:

• Happy Chick runs on Android, iOS and Windows and covers more than 18 game consoles, making it a broader console-oriented option.
• MAME is free on Android, Linux, macOS and Windows; ROMs and copyrighted software are generally not included.
• RetroArch supports Android, iOS, Linux, macOS, web and Windows. It is a long-running open-source project.
• VICE is free software under GNU GPL v2 or later and supports Android, Linux, macOS and Windows.
• AmiArcadia/WinArcadia is open-source freeware for Android and Windows, with AmigaOS versions also identified for AmiArcadia.
• Dolphin is a free GPLv2+ emulator for Android, Linux, macOS and Windows; distributing it requires source release and attribution.
• EmulatorJS is a free, ad-free, open-source option for Android, iOS, web and self-hosted use.
• FinalBurn Neo is free and open source for Android, Linux, macOS and Windows, but it cannot be sold or used for monetary profit and ROM images require legal distribution rights.

Verdict

Choose openMSX if you want detailed MSX-family emulation with serious debugging, scripting and reverse-playback tools, and are willing to configure the machine you need. Its breadth and price are compelling; look elsewhere if you need a current Android release or want a complete machine setup with less configuration.