When the round stutters, close what first
A sensible order of actions when a round stutters: video, downloads, extensions, then the network.
The first step is to separate two problems that look alike. If the game is slow to appear in the first seconds, that is loading: files are still travelling, and ten seconds of patience may be enough. If the game is already on screen but the character moves late after a key press, that is lag: data is going out and coming back over the network, and closing other tabs will help more than waiting.
Close video tabs first. A single tab playing video, even in a small window behind the browser, spends processor time and bandwidth at once. Stop the video, close its tab, then play one round before doing anything else. In many cases that one step is enough, and there is no reason to work through the rest of this list if the round is already smooth. Always test before adding another change.
After video, look at downloads and updates. An operating system pulling a large update will use the connection without telling anyone. Open the browser download manager and the system update panel, pause whatever is running, and let it finish after you play. This matters most in the evening, when updates are scheduled automatically and nobody remembers agreeing to them. If the panels show nothing obvious, open the task manager and watch the network column for ten seconds; the busiest process is usually the one worth pausing before the next round.
Next, browser extensions. Every extension reads page content or injects code, and some check every link on every page. On a new machine the cost is invisible; on an old one it is the difference between a smooth round and a stuttering one. The cleanest fix is a separate browser profile with no extensions at all, used only for playing. That profile also keeps your work tabs out of sight.
On wireless, distance and frequency band matter more than the speed printed on the box. If the router broadcasts two bands, join the five gigahertz one at short range, because it is less crowded even though walls block it more easily. Do not hide the router behind a television or inside a metal cabinet. If a cable is available, use the cable; one wire removes this entire category of problem.
In the browser, close developer tools if they are open, because that panel collects information on every frame. If you once turned off hardware acceleration for other work, try turning it back on and compare one round. Some old machines are smoother without it and some are worse; there is no general answer, so test one setting at a time and write down the result. Guessing is what makes people buy hardware they did not need.
Inside the game, lower graphics quality and switch off unnecessary effects before reducing resolution. Resolution has the biggest effect on the graphics processor, but it also blurs text and direction markers. Start by turning off shadows and particles, then drop resolution one step. Full screen helps as well, because the browser no longer has to draw an interface around the play area. Text stays readable at full screen even when the resolution is lower.
Finally, change one thing at a time and test with a complete round. Closing five tabs, switching band and lowering quality all at once gives you a smooth round without telling you which change did the work, and next week you will repeat the whole list. One change, one round, one short note. That is how a machine stays playable without anyone buying new hardware to solve a problem caused by three open tabs.