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If a receptacle has a ground slot, it needs a working ground — unless you use one of the code-allowed fixes for old wiring, like a GFCI marked 'No Equipment Ground.'

The worst thing I find is a three-prong outlet screwed onto two-wire cable with no ground at all. Someone did it to fit a plug, and now the whole circuit lies about being safe.

When it applies

Grounding-type receptacles must actually be connected to an equipment grounding conductor. When you replace a receptacle in an older box that has no ground, the Code gives you defined options rather than leaving you stuck.

Common mistakes

• Installing a three-prong receptacle on ungrounded wiring with no GFCI protection and no label. That fools people into trusting a ground that is not there.
• Bootlegging a jumper from neutral to ground to fake continuity. Dangerous and prohibited.
• Forgetting the required no-equipment-ground labels when you use the GFCI option.

In the field

In a 1950s house I found three-prong outlets everywhere with no ground behind them. Somebody swapped them to fit modern plugs. I put GFCI protection ahead of them and applied the labels the Code requires, so the outlets are safe and honest about what they offer. If you cannot ground it, protect it and label it.