Which wire should I use to use USB port as a power supply?

[mehboob_iiui]

if you plug a usb connector in a port you get four wires, which ones should be used if one wishes to use it as a small power supply,

 

[M!k]

Re: USB port power

Check the USB specification:
https://www.usb.org/developers/docs/usb_20_040907.zip
5V and Gnd are the outer lines.
Btw. in this situation (without enumeration) the current must be < 100mA !