Demo of the audacity of Javascript-based beam racing. Only successfully tested on Windows in Chromium browsers, using a special command line.
You may copy and paste this Windows command line for convenient startup of Chrome in VSYNC OFF mode:

"C:\\Program Files\\Google\\Chrome\\Application\\chrome.exe" --user-data-dir=c:\\windows\\temp\\vsync-off --disable-gpu-vsync --disable-frame-rate-limit https://testufo.com/raster51

Still being implemented. A localhost WebSocket proxy needs to be implemented to communicate between a VSYNC ON and a VSYNC OFF browser processes.
For now, please follow Option 2 instead, which works.

1. Temporarily use SINGLE MONITOR (disable multimonitor) and LOWER REFRESH RATE at 60 Hz or less for more accurate beam racing.
2. Run this command to create a localhost websocket relay: (TBD)
3. VSYNC ON browser process: Keep your first launched instance of this URL running; It becomes the VSYNC ON instance, for precise refresh cycle timing.
4. VSYNC OFF browser process: Launch using the above command line to create a 2nd independent browser process in VSYNC OFF mode, for the beam racing effects.
5. The localhost websocket relay server, communicates the refresh cycle timing information from the VSYNC ON browser process to the VSYNC OFF browser process.
6. If tearing correctly at over ~1000fps, Kefrens Bars appears in ~5 seconds (stops rolling like mis-adjusted VHOLD), and beamrace failure message disappears.

1. Temporarily use SINGLE MONITOR (disable multimonitor) and LOWER REFRESH RATE at 60 Hz or less for more accurate beam racing.
2. Wait for refresh rate to be detected. Alternatively, use TestUFO Refresh Rate.
3. Configure your GPU and operating system to permit VSYNC OFF.
       NVIDIA Control Panel -> Manage 3D Settings -> Global -> Vertical Sync -> "Use 3D Application Setting"
4. Relaunch Chrome using blue command line above.
5. If necessary, manually enter exact refresh rate of your display. Animation works best at low Hz.
6. Hit F5 at least twice to refresh the page. This helps power management settle down to high frameslice rate.
7. Click full screen button in upper-right corner of animation.
8. If animation is misaligned vertically, use mouse to drag white bar (VBI) to top or bottom of screen.
9. If tearing correctly at over ~1000fps, you will see wavy lines (video) & mouse softcursor will have less lag than OS mouse pointer.

TIPS ON SYSTEM SETTINGS:This animation performs best at lower refresh rates (24Hz or 60Hz), in Performance Mode (not Balanced Mode), on Windows systems with AMD/NVIDIA GPUs, with MSI Afterburner forcing a high idle GPU clock rate. Modern high performance GPUs (GTX 1080 and newer) should be able to achieve 2000-4000fps on i7 CPUs. Currently only tested on Windows systems with high performance NVIDIA GPUs. For more information on this new browser beamracing feat, see pouet.net thread and vogons.org thread #1 / thread #2, as well as our github open source RefreshRateCalculator.js