Download
Unpack it, start it on the monitor you want to test and press ENTER. Bzzrt reads the monitor's VRR range from
its EDID. If it can't find one, or the detected range is wrong, you type in the range before the test starts
(see QUICKSTART). Checksums, release notes and older versions are on the
releases page.
Arch Linux and derivatives (CachyOS, EndeavourOS, Manjaro): install the package from the table with
pacman instead of unpacking anything. This adds vrrdiag (also as bzzrt) and a
"Bzzrt" app-menu entry.
sudo pacman -U https://github.com/Prajwaljb/Bzzrt/releases/download/v1.1.1/bzzrt-1.1.1-1-x86_64.pkg.tar.zst
Or build it yourself from packaging/aur/PKGBUILD:
git clone https://github.com/Prajwaljb/Bzzrt.git
cd Bzzrt/packaging/aur && makepkg -si
What it does
vrrdiag generates controlled presentation timing (exact frame intervals, scripted
rate switches, frame-time spikes and jitter) so you can find out whether VRR flicker comes from:
- low framerate compensation (LFC, frame multiplication below the VRR floor),
- individual frame-time spikes,
- transitions between normal VRR and LFC, or
- something unrelated to VRR (cable, link, panel, overdrive, FRC).
It is a native application on every platform:
| Platform | Backend | Presentation path |
|---|
| Windows 10/11 | Direct3D 12 (default), Direct3D 11 fallback | DXGI flip model (FLIP_DISCARD), ALLOW_TEARING, frame-latency waitable |
| Linux | Vulkan WSI on Wayland or X11 | FIFO / FIFO_RELAXED / MAILBOX / IMMEDIATE, VK_KHR_present_id + VK_KHR_present_wait, VK_GOOGLE_display_timing |
| Linux (advanced) | Direct DRM/KMS from a text console | atomic page flips with VRR_ENABLED controlled by the app, kernel flip timestamps |
| macOS 12+ (Apple silicon) | Metal on a CAMetalLayer | native fullscreen, displaySyncEnabled, MTLDrawable.presentedTime |
Software cannot prove that the monitor is in VRR or LFC. The app knows exactly when it
submitted each frame and, where the driver exposes it, when the OS/driver says the frame was
presented. It cannot see what the panel actually scanned out. Watch the monitor's OSD refresh
readout, or film the screen with a high-speed camera, to confirm what the panel is doing.
See docs/VRR_LFC_GUIDE.md.
Common questions
Why does my FreeSync or G-SYNC Compatible monitor flicker at low FPS?
Below the monitor's VRR minimum (often 48 Hz) the panel cannot hold a frame any longer, so the driver must show frames
twice or more (low framerate compensation, LFC), or the panel forces a repeat on its own. Many panels, VA panels in
particular, change brightness with how long each frame is held. Entering and leaving LFC therefore shows up as
flicker. Bzzrt runs steady and switching tests on both sides of the minimum so you can see where it starts.
Is VRR flicker a defect of my monitor?
It depends on when it happens. Flicker at a steady frame rate inside the VRR range, while the computer delivers
evenly timed frames, points to the monitor. Flicker only when the frame rate crosses the minimum, or only when the frame
timing is uneven, is a known VRR side effect or a driver / compositor problem. Bzzrt measures the timing and tells you
which case you have.
How do I find my monitor's VRR range?
Bzzrt reads it from the monitor's EDID (FreeSync data block, DisplayID Adaptive-Sync, HDMI VRR or range limits) and
shows it on the start screen. If it is missing or wrong, press R and type the range from the spec sheet.
Does it work on Linux and Wayland?
Yes. It uses Vulkan on Wayland (KDE, GNOME, Hyprland, Sway) and X11, plus an optional direct DRM/KMS mode that bypasses
the compositor. Windows uses Direct3D 12 and macOS uses Metal.
1. Building
Requirements: CMake ≥ 3.16 and a C++17 compiler. There are no third-party libraries beyond the OS and graphics SDKs.
Windows (Visual Studio 2022, Windows 10/11 SDK)
From a "Developer PowerShell for VS 2022" (or any shell with CMake):
cmake -S . -B build -G "Visual Studio 17 2022" -A x64
cmake --build build --config Release
.\build\Release\vrrdiag.exe --help
Ninja works as well (cmake -S . -B build -G Ninja -DCMAKE_BUILD_TYPE=Release from a VS developer prompt).
The executable links the CRT statically and needs only d3d12.dll, dxgi.dll and d3dcompiler_47.dll, which ship with Windows.
-DVRRDIAG_D3D11=OFF drops the D3D11 fallback.
Linux
Install the development packages:
This is the beginning of the README. Read the rest at the original. Read the full README ↗
