A zero-ohm link or zero-ohm resistor is a wire link used to connect traces on a printed circuit board that is packaged in the same format as a resistor. This format allows it to be placed on the circuit board using the same automated equipment used to place other resistors instead of requiring a separate machine to install a jumper or other wire. Zero-ohm resistors may be packaged like cylindrical resistors, or like surface-mount resistors.
One use is to allow traces on the same side of a PCB to cross: one trace has a zero-Ohm resistor while the second goes in between the leads of the resistor. A second use is as a configuration resistor. Zero-Ohm link may be used as an ad-hoc kind of a fuse.
The resistance is only approximately zero; only a maximum (typically 10–50 mΩ) is specified. A fractional tolerance would not make sense, as it would be specified as a percentage of the ideal value of zero ohms and a fraction of zero denominator is an undefined operation, so it's not specified.
An axial through-hole zero-ohm resistor is generally marked with a single black band, the symbol for 0 in the resistor color code. Surface-mount resistors are generally marked with a single "0" or "000".
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