Is it safe to use third party battery and battery grips?

I'm planning to buy extra battery and a battery grip for my nikon d5200.Is it safe to use third parties? Will it harm the dslr on the future? And if not, what brands do you guys prefer?

I'd hunt down the reviews first and see what issues others have with them. Generally third party grips are not manufactured to the same standard as the original manufacturers grips (in this case Nikon).

I have used a battery grip in the past, but frankly haven't bothered getting one for my current camera.

Generally they will not damage your camera - unless you have it on a tripod and the camera breaks off the grip. Some of the 3rd party grips are rather weak - they may use plastic mounting posts, where the OEM grips use metal posts. So be sure you are getting a well-built grip.

But usually they don't have the functionality that the OEM grips have, such as simultaneously using both batteries, shutter and command dials, etc.

Since you usually can't use both batteries at the same time, the grip more or less just becomes a battery storage compartment, and you have to swap the batteries anyway, so why not just carry the spare battery in your pocket or camera bag and save yourself the extra weight on your neck.

I used to have a Nikon grip for my D90, and the only time I used it was when I used my AF 80-200mm f/2.8. This is a heavy lens and the extra weight helped balance the lens. Otherwise, it was just too heavy. When I upgraded to my D7100, I sold the grip (as it would not fit), and I see no reason to buy another as I really didn't use it often.

Otherwise, using a grip just adds weight, and unless you need it for a specific purpose, it kind of looks silly - especially on an entry level camera.

Rule of thumb, don't put non Nikon products on a Nikon body except for a lens. Nikon batteries are special, and the camera can often tell when a non Nikon battery is put in it.