Cat-5 cable, sometimes called Ethernet cable, is short for Category 5 cable, a current industry standard for network and telephone wiring. Cat-5 cable is unshielded wire containing four pairs of 24-gauge twisted copper pairs, terminating in an RJ-45 jack. If a wire is certified as Cat-5 and not just a twisted pair wire, it will have "Cat-5" printed on the shielding.

The outer sheath of Cat-5 cable can come in many colors, with bright blue being quite common. Inside, the twisted pairs are also sheathed in plastic with a standard color scheme: Solid orange, blue, green and brown wires twisted around mates that are white and striped with a solid color. The twisted pairs inside a Cat-5 cable reduce interference and crosstalk, and should be left twisted except at the termination point. Some experts recommend untwisting only ½ inch (12.7 mm) of the pairs to strip and make connections. Cat-5 cable can be purchased off a spool in varying lengths, or bought pre-cut to standard lengths with RJ-45 jacks already attached.

Cat-5 cable replaces Cat-3 cable, which could only carry data at speeds up to 10 megabits per second (mbps), while Cat-5 cable supports data speeds of 100 mbps or more. A standard Cat-5 cable can also reach 300 feet (100 meters), and aside from networks and telephones it can be used for many other purposes. Cat-5e is enhanced Cat-5 cable that supports 1000 mbps or gigabit Ethernet, or it can be used with 100 Base-T networks for long-distance runs of 1150 feet (350 meters). This type of Cat-5 cable meets a specific standard referred to as "EIA/TIA 568A-5," which should be stamped on the outer sheath.

Among Cat-5 cables, there are three different configurations for pinouts, or wiring of the RJ-45 connectors. Various network devices utilize one of the three types of pinouts. The three pinouts are referred to as straight through, crossover and roll-over.

The Cat-5 cable that runs from a computer to a switch will be a straight through cable, for example. If two PCs or two switches are connected, the Cat-5 crossover cable would be used. Finally, a Cat-5 roll-over cable will connect a PC to a router. More recent devices, however, can detect the type of Cat-5 cable being used and route signals accordingly.

Cat-5 cable is available everywhere wiring is sold, including electronics shops, home improvement centers, and computer outlets. It is also widely available online. Note that a newer Cat-6 cable will eventually replace Cat-5, having twice the bandwidth.