The ATX 24-pin power connector is the standard motherboard power connector in today's computers. The connector itself is a Molex 39-01-2240 connector, often referred to as a Molex Mini-fit Jr.
How to Use an ATX Power Pin Removal and Extraction Tool: 24-Pin, 8-Pin, 6-Pin, 4-Pin.
Below is the full pinout table for the standard ATX 24-pin 12V power connector from version 2.2 of the ATX specification (PDF).
The pinouts for the 15-pin SATA power connector, 4-pin peripheral power connector, 4-pin floppy drive power connector, and other ATX power connectors can be viewed in our ATX power supply pinout tables list.
The power connector can only be connected while it is pointing in a specific direction on the motherboard. If you look closely at the following illustration, you will see that the pins take on a unique shape, which matches the motherboard in only one direction.
