Most people can tell the difference between a grounded and ungrounded wall receptacle at a glance. In the US, a grounded wall receptacle will have 3 holes in it, while an ungrounded receptacle only has 2. But does seeing a receptacle with 3 holes in it necessarily mean that your outlet is properly wired? Not always. Some homeowners have installed a grounded wall receptacle to replace an ungrounded receptacle without having the proper wiring. To check if this is the case, you would need to use specialized equipment to test it. Fortunately, this can be purchased at most hardware stores fairly inexpensively, however, these devices aren’t going to tell you the quality of the ground.
If your home isn’t wired for ground, which might be the case in older homes, you could install a GFCI receptacle to compensate for this. Without a proper ground or a GFCI outlet, you risk getting electrocuted by a faulty appliance.