MangoHud is a Linux-first, in-process performance monitoring overlay for Vulkan and OpenGL games. It injects a HUD that shows FPS, frame times, CPU/GPU load, temperatures, clocks, power, VRAM/RAM usage, I/O, network, battery, and media player metadata. The code implements this through multiple low-level integration paths: a Vulkan implicit layer, OpenGL/EGL/GLX swapchain hooks, LD_PRELOAD shims, a gamescope companion app (mangoapp), and a Windows DLL path that uses kiero to hook D3D11/D3D12 and DXGI. Hardware metrics are collected from Linux sysfs/proc interfaces, vendor libraries like NVML and XNVCtrl, and vendor-specific DRM/hwmon backends for AMD, Intel, NVIDIA, Panfrost/Panthor, and Qualcomm GPUs.