Two things we find wrong on a lot of gaming PCs, both free to fix: a 144 or 240 Hz monitor that Windows left at 60 Hz, and a gaming mouse reporting at 125 Hz instead of 1000. Ten seconds each, right here.
Your browser draws once per screen refresh, so timing it for two seconds tells you the rate Windows is actually running this screen at.
Keep this tab in front and the window on the screen you play on, then press the button.
Settings › System › Display › Advanced display › Choose a refresh rate: pick the highest. If it is not offered, the cable or port is the limit: use DisplayPort, or the HDMI cable that came with the monitor, plugged into the graphics card rather than the motherboard.
OmniDx Tune's app finds this for every screen and fixes it in one click, then asks you to keep it: nothing answered in 15 seconds goes back by itself.
A laptop on battery saver, or a browser told to save power, can draw at a lower rate than the screen runs: plug in and try again.
How often the mouse tells the PC where it is. At 125 Hz a movement can wait up to 8 ms to be sent; at 1000 Hz, 1 ms.
Press the button, then move the mouse quickly in circles over the box for four seconds.
Most gaming mice ship at 1000 Hz but some come at 125 or 500. The setting is in the mouse's own software (or a button under the mouse): set 1000 Hz. 2000 Hz is fine on a recent CPU; 4000 and 8000 Hz cost CPU time on every report, and if a game stutters with them, 1000 is as good to the eye.
Browsers read the mouse through their own event system, so above about 1000 Hz this page can read low. The OmniDx Hub (with OmniDx Edition, included with OmniDx Tune) reads every report Windows hands over.
The free look runs in PowerShell, changes nothing, and reports what is slowing this PC: the processes running, the memory speed against its rating, every screen's refresh rate, the graphics driver's age, the page file, the drive.
Right-click Start, open Terminal (or PowerShell), paste:
irm omnidx.net/go.ps1 | iex
No key, no account. Read the script first if you like.
The full list, free: the BIOS, Windows' settings, the graphics driver's control panel, and the myths to skip. Do it by hand.