jagt/clumsy
Freeclumsy makes your network condition on Windows significantly worse, but in a controlled and interactive manner.
FreeFree tier
About jagt/clumsy
clumsy is an open-source tool for Windows that simulates poor network conditions by intercepting network packets using WinDivert and applying effects like lag, drop, tamper, and packet loss on demand. It requires no installation or proxy setup, works system-wide with any application (including localhost traffic), and provides interactive controls with visual feedback. Ideal for testing application behavior under broken, slow, or unreliable connections. The tool is licensed under MIT and runs on Windows 7/8/10.
Key Features
System-wide network packet capturing using WinDivert
No installation or proxy setup required
Works offline (localhost to localhost) without an internet connection
Interactive control with visual feedback for effects
Simulate latency, delay, packet loss, and packet tampering
Start and stop anytime without restarting the target application
Operates on Windows 7/8/10
Free and open source under MIT license
Pros & Cons
Pros
- Free and open source (MIT license)
- No installation or code changes needed to test applications
- Works system-wide with any application, including offline/localhost
- Interactive and visual control over network conditions
- Lightweight and does not require restarting the target application
Cons
- Windows only (does not support macOS or Linux)
- Requires WinDivert driver, which may need administrator privileges or manual installation on older systems
- Only manipulates network-layer packets; cannot simulate higher-level protocol behaviors
- Limited to packet-level effects (no emulation of bandwidth throttling or jitter at application layer)
Best For
Testing application behavior under poor network conditions (high latency, packet loss)Debugging network-related bugs in applicationsEvaluating software resilience on broken or unreliable connectionsSimulating real-world network degradation scenarios during development
FAQ
What is clumsy?
Clumsy is an open-source Windows tool that intercepts network packets and applies controlled effects like latency, packet loss, and tampering to test applications under poor network conditions.