Some laptop models provide an additional RAM slot to allow you installing a new RAM. But before you buy a new RAM, you need to make sure that the RAM you want to buy has the same specs as the RAM already installed on you laptop.
How to check the specs of the installed RAM?
In Windows 10 (and other Windows versions), the most common way to check the specs of the installed RAM is by checking the System Properties. However, the displayed information on System Properties is not detail enough. The only information you get is the RAM capacity. There is no information about RAM speed and form factor.
To check the speed of the installed RAM in Windows 10, you can open Task Manager instead of System Properties. In addition to speed, you will also find other information regarding the installed RAM like form factor, the used slots, current RAM usage and so on.
Open Task Manager (Ctrl + Shift + Esc) and click the More details button to expand its window.
On the Task Manager window, click the Performance tab and select the Memory section. As you can see, there are some more detailed information about your RAM, including the speed which lies beneath the graph.
Installing a new RAM with the lower speed than the installed RAM can cause your laptop to be under performance. Your system might recognizes the newly installed RAM, but it can make your laptop runs slower because the first installed RAM will follow the lower speed.