OpenSpeedy
🎮 An open-source game speed modifier.
A free Windows tool that hooks time functions to speed up or slow down a running game, intended for single-player research, not competitive online play.
OpenSpeedy is a free, open-source tool for Windows that lets you change the speed at which a game runs. You pick a game that's already running, set a speed multiplier in the OpenSpeedy interface, and the effect kicks in immediately — making the game move faster or slower than normal.
It works by intercepting ("hooking") the time-related functions that Windows and games use to measure elapsed time, effectively tricking the game into thinking time is passing faster or slower. This happens at the application level rather than by modifying the operating system itself, which means it doesn't touch system files. It supports both 32-bit and 64-bit games and requires Windows 10 or later.
The tool is built in C++ using the Qt framework for its interface. You can install it via winget (Windows' built-in package manager) or download it manually from the releases page.
Important caveats stated in the README: this tool is intended for learning and research purposes only. Online games with anti-cheat systems may ban your account if you use it. Speeding up a game too much can cause the physics engine to break or crash. The authors specifically say it is not recommended for competitive online games.
Where it fits
- Speed up a slow single-player game to skip grind
- Slow a game down to study its physics or animation
- Learn how to hook Windows time APIs from a C++ Qt app