CPU slows after starting a video call? How to test

Your video call starts smoothly, but after a few minutes the picture stutters, the fan gets louder, or other apps feel slow. A call adds work for your processor, especially when you use a camera, background effects, or screen sharing.

Compare CPU performance before and during a low-stakes call, then check whether heat causes a further slowdown. The browser tests show relative performance, not an exact CPU temperature or a diagnosis of every call problem.

Compare CPU performance before and during a call

1. Open the Processor Test and run the same test before starting a call. Note the single-core and all-core scores.
2. Keep the computer in the same place and on the same power source. Close unrelated apps, but leave open anything you normally use during a call.
3. Start a practice or low-stakes video call. Use the same camera, effects, and screen sharing you use when the slowdown happens. Let the call run for 5 to 10 minutes.
4. While the call is still running, repeat the same Processor Test. Watch for a drop in the score and note whether the call becomes choppy during the test. A CPU test adds extra work, so do not run it during an important meeting.
5. End the call, then run the Overheating Test separately. It puts the processor under full load for a few minutes to check whether performance falls as the computer heats up. Stop if the computer becomes unusually hot or unstable.

For a useful comparison, change one thing at a time. For example, test once with a virtual background and once without it. Scores can vary with browser, power mode, and background activity, so compare runs on the same computer and in the same browser.

What the results mean

The scores stay close during the call

The processor test did not show a large loss in throughput, which is the amount of work the CPU completes in a given time. The call may still stutter because of Wi-Fi, the camera, the call service, or another part of the computer. If the main symptom is a falling CPU clock during a call, see how to check CPU clock drops during a video call.

The score falls while the call is active, then recovers

The call and test are sharing the processor. A lower score means less CPU capacity was available to the test at that moment, but it does not by itself prove a fault. Video effects, screen sharing, browser tabs, and other apps can all compete for time on the CPU.

The Overheating Test score drops as it runs

A decline under a sustained full load can mean the computer is reducing performance as it warms up. This is called thermal throttling. The test can show a performance change, but a browser cannot read the exact CPU temperature or tell you which cooling part is responsible.

Scores vary between runs, with no steady pattern

Short benchmark runs are affected by background work and power settings. Close updates, file transfers, and other heavy tasks, wait a few minutes, and repeat the comparison. A single low score is not enough to call the CPU faulty.

How to reduce the slowdown

1. Reduce call effects. Turn off background blur, virtual backgrounds, and other visual effects, then test again. These features can add processing work, particularly on a thin laptop.
2. Close unnecessary apps and tabs. Pause downloads, video playback, and large file transfers. Keep the call app open, but avoid running several demanding tasks at once.
3. Use a suitable power mode. On Windows 11, open Settings › System › Power & battery › Power mode and choose a performance-focused option when plugged in. On a Mac laptop, check System Settings › Battery and turn off Low Power Mode for the comparison if it is enabled.
4. Give the computer room to cool. Place a laptop on a hard, flat surface, keep vents clear, and do not use it on bedding. If the fan is clogged with dust, follow the manufacturer's cleaning guidance rather than pushing tools into the vents.
5. Check whether the call app is the trigger. Try the call in another supported browser or the app's desktop version, if available. Keep the camera and call settings as similar as possible, because changing the setup can change the processor load.

When to suspect a cooling or hardware problem

A small score change during a call is normal. A repeatable decline during the Overheating Test, combined with strong fan noise, frequent stuttering, or shutdowns, is more concerning, especially if vents are clear and the computer is not in a hot room. The test cannot identify a failed fan or confirm a temperature limit. If performance keeps collapsing under ordinary use, back up important files and contact the manufacturer or a repair shop. A laptop under warranty should be checked before you open it.

Do not run a full-load test repeatedly just to force a result. One careful run, followed by a comparison after the computer cools, is usually more useful.