How to detect CPU slowdown without temperature readings

Your computer may feel fast at first, then slow down after a few minutes of gaming, video editing, or another demanding task. You can check for this kind of decline even if you cannot see the CPU temperature.

The Overheating Test puts the processor under a sustained load for a few minutes so you can see whether performance falls. Repeat the test under the same conditions to check whether the change is consistent.

Test for performance decline

Open the Overheating Test. Save your work first, since a full processor load can make the computer temporarily less responsive.
Set up a fair test. Plug in a laptop, place it on a hard surface, and leave the vents clear. Close games, video editors, and other heavy programs, but keep the browser tab with the test open.
Run the test for its full few-minute period. Watch whether the measured performance stays steady or drops as the test continues. A loud fan by itself does not mean performance has fallen.
Let the computer sit idle for 10 to 15 minutes, then repeat the test without changing its position, power connection, or settings. A similar drop on both runs is more useful evidence than a single result.
For a numeric comparison, run the Processor Test while the computer is cool and note its score out of 100. Run it again just after the sustained-load test. Keep other conditions the same, and treat the scores as a comparison of this computer with itself, not as a universal pass mark.

What the result means

Performance stays about the same

The computer did not show a clear performance decline during this short test. That is reassuring, but it does not rule out a problem that only appears during a longer gaming session, in a warmer room, or with a different workload.

Performance drops toward the end, and it happens again

A repeated decline under sustained load is a sign that the computer is reducing performance or changing its power limits. Heat can cause this behavior. So can a power-saving setting or a power adapter that is not supplying enough power. The test shows what performance does, not which cause is responsible.

The result changes from one run to the next

Background tasks, a different power mode, or a change in room temperature can affect the result. Close demanding apps, use the same power connection, and repeat the test after the computer has cooled. If only the Processor Test score varies, small differences between runs may be normal.

The computer is slow, but the test result is steady

The slowdown may be specific to one app, a full storage drive, limited memory, or a network delay rather than processor performance. Check whether the problem happens in other programs too before treating it as an overheating issue.

How to reduce performance drops

Close other demanding programs. Pause downloads and close games, video editors, and extra browser tabs before testing. Background work can compete for processor time and make results harder to compare.
Check the power mode. On Windows 11, open Settings › System › Power & battery › Power mode and choose Best performance for a fair test. On macOS, open System Settings › Battery and check whether Low Power Mode is enabled for the current power source. Turn it off while comparing performance.
Use the correct charger. Connect the laptop to its original charger, or one with the wattage recommended by its manufacturer. Some laptops limit performance when they run on battery or detect an underpowered adapter.
Give the vents room to breathe. Use the computer on a desk instead of a bed, blanket, or lap that can block its air intake. Keep it away from direct sunlight and other heat sources.
Check for dust and fan problems. Look for dust covering the vents and listen for a fan that rattles, grinds, or never spins up under load. Follow the manufacturer's cleaning instructions. If opening the case could affect your warranty, do not take it apart.
Restart and retest. Restarting can stop a stuck background process from using the processor. Install system updates when convenient, then repeat the same test setup to see whether the decline remains.

When it may be a hardware problem

Consider a repair if the performance drop happens repeatedly after you have cleared the vents, used the right charger, and checked the power mode. A fan that does not run under load, a grinding fan, or a computer that shuts down during the test needs more attention than a small score difference. If the computer is under warranty, contact the manufacturer before opening it. Otherwise, a repair shop can inspect the fans, cooling system, and power delivery.

Why the test works without a temperature reading

A browser may not be able to read the processor's exact temperature. Instead, this check looks at performance while the processor is busy. If performance falls as the computer warms up, that is a clue, not proof, that heat is the cause. Power settings and background work can produce similar changes. For more on what browser checks can and cannot detect, see what a browser-based hardware check cannot detect.

The tests run on your device, and you do not need to install an app to compare the results.