Fixing TestUFO "Stuck at 30Hz or 60Hz" problems
Aka: "TestUFO not working at 144Hz", "TestUFO not working at 120Hz", "TestUFO running oddly 360fps at 480Hz"
Web browsers are very sensitive to stutters. TestUFO demands high performance for perfect stutter-free operation. Most web browsers often are stubborn at running at the correct refresh rate, and often stays stuck at 60fps even if you're at a high refresh rate. Unfortunately, web browsers are a very finicky beast, and is often impossible to detect the correct refresh rate in certain web browsers; ending up saying "60Hz" when it is actually 120Hz or 144Hz. That can often happen due to many causes. Several tips are listed at http://www.testufo.com/browser.html but this thread documents more tips.
There are frequent comments about TestUFO being "stuck at 60Hz".
Here are the common solutions:
Temporarily Turn off Multiple Monitor Mode: Don't Mix Two Refresh Rates
Multiple monitors running at different refresh rates, often interfere with correct TestUFO refresh rate. Close laptop lid when using laptop to run TestUFO on external displays. Alternatively, make all your monitors all equal to the highest refresh rate, or instead disable multi-monitor. The highest-Hz monitor must absolutely be the primary display, with nothing running on secondaries.
Doublecheck Windows Control Panel
Before following the next steps, verify your monitor is actually running Windows above 60Hz first. You probably already did this, but please doublecheck first before the next step, since sometimes drivers, OS, or monitor EDID defaults reverts to 60Hz automatically. Follow the instructions in Oh No, I Am At The Wrong Refresh Rate 
Apple 120Hz+ Requires Custom Settings Change
Please turn off "Prefer Page Rendering Near 60fps" setting in your Safari browsers' Developer menu. All 120Hz Apple devices running iOS 18 will work with TestUFO at 120fps, after this setting change. Certain devices (older 120Hz iPads and older 120Hz MacBooks) will work with Safari version 17, however, more universal 120Hz Safari support requires iOS 18. See www.testufo.com/browser.html for recommended minimum versions. TestUFO will run fine at 240Hz on MacBooks M1+ connected to 240Hz displays (use USB-C port), see photo, even on multimonitor (Mac surprisingly does "different-Hz" multimonitor better than Windows does!?).
Exit your RGB Software & CPU Monitoring Software
While this usually does not cause a stuck-at-60Hz problem, it can add red spikes at www.testufo.com/animation-time-graph that corresponds to TestUFO stutters. Exit/uninstall inefficient background RGB software (e.g. Aorus Gigabyte's 2023-era RGB software added stutters to games, newer might be better). Also, CPU monitoring software like Task Manager can add stutters to TestUFO. Exit Task Manager to avoid stutters.
Mobile Devices Running at 30-60Hz In Battery Saver Mode
Battery Saver Mode may reduce the browser frame rate or refresh rate. Please recharge your battery or plug your device into a power outlet.
Laptops Connected To Gaming Monitors
Such as a 144Hz monitor connected to a 60Hz laptop. Close the laptop lid and make the 144 Hz monitor the primary and only monitor. Plug laptop into AC outlet to exit Power Saver mode.
Use Aero Mode. Don't Use "Windows Basic Mode"
If you're using Windows 7, don't use "Windows Basic Mode". If you're using Windows Vista, don't turn off "Aero".
Try Using Different Browser
TestUFO is currently optimized to work very well with Google Chrome. IE only runs up to 105Hz, while Chrome runs reliably at 240Hz (if no other applications are running). FireFox also works well (with the stutter fix below).
Fixing Chrome Stutters
Try quitting all applications and windows. Pause your cloud sync (Dropbox) and other background apps. Temporarily reboot in Safe Mode (but enable the graphics driver).
Fixing FireFox Stutters
Occasionally, there are situations where a specific computers only runs 60Hz Chrome but has correct Hz in FireFox. However, FireFox often stutters quite a lot at high refresh rates until you temporarily set minimum CPU to 100%. When adjusted this way, it successfully runs at all current refresh rates.
Check chrome://gpu
Make sure everything is hardware accelerated. Sometimes Chrome will go into software rendering mode that has a 60fps cap.
Check chrome://flags
Sometimes GPU acceleration is disabled. Try enabling GPU acceleration.
Test Balanced Mode or Performance Mode
Power-saving mode may force a browser into a 60Hz mode even with laptops connected to an external display.
Upgrade Graphics Drivers
Sometimes certain web browsers blacklists certain graphics drivers from properly working at full frame rate. A graphics driver upgrade may fix this.
Retest Two Browsers Again
Try both FireFox and Chrome again after you've done all the above (settings tweaks, driver upgrades, etc). Occasionally, one of two web browsers suddenly runs at above 60fps -- so it's best to cover all bases.
Test using native Windows. Don't use a Virtual Machine
Virtual Machines are often stuck at 60Hz. If you are using Parallels or VMWare, please retest natively rather than inside a VM or emulator. Windows works best with TestUFO.
Full frame rate but FAILED SYNC?
Try restarting to a clean Windows Desktop without any background apps, including system tray apps. System tray software can sometimes be the cause. For example, certain brands (not all) of RGB software can cause GPU/latency spikes that interfere with TestUFO ability to sync.
Exit Task Manager and other Monitoring Utilities
Monitoring software such as Task Manager, will inject approximately millisecond-scale freezes into the system. This wasn't a problem in 60Hz days, but is more of an issue with 240Hz+ when a millisecond is 25% of a 240Hz refresh cycle. Exit all monitoring software including software that displays statistics on tiny screens (computer tower screens, heatsink screens, etc). This fancy frosting is fun to look at but should be temporarily disabled during critical esports gaming.
Success? New tips?
Please post what tip fixed your "Stuck at 60Hz" problem. Additional tips will help many users!
Failure?
If you have failed to figure out what to do, please do the following
1. Copy and paste the browser useragent found at bottom of http://www.testufo.com/browser.html
2. Screenshot your Control Panel -> Display refresh rate (or Custom Resolution Utility screen)
3. Screenshot your animation time graph from http://www.testufo.com/animation-time-graph
4. Mention which web browsers you have already tested (retest all browsers after trying all fixes)
