RJ45 is the common name for the 8-position, 8-conductor (8P8C) connector used on Ethernet cabling. It is the small rectangular plastic plug at the end of a standard network cable, with eight gold-plated conductors arranged in a row and a sprung locking tab that holds it in place when inserted into a socket.

In short: RJ45 connectors are used on twisted-pair Ethernet cables of all categories: Cat 5e (up to 1 Gbps), Cat 6 (1 Gbps reliably and 10 Gbps over shorter distances), Cat 6a (10 Gbps), and beyond. The pin assignments follow either the T568A or T568B wiring standard (functionally identical, but installations should pick one and use it consistently). RJ45-terminated cables come in two main variants: stranded patch leads for connecting devices to wall sockets or switches, and solid-core structured cabling for permanent installation behind walls and through cable trays.

For industrial IoT, RJ45 connectors come in standard and ruggedised variants. Standard RJ45 plugs are fine for indoor, controlled environments. Industrial deployments in vibration, dust, or moisture conditions often use either shielded RJ45 (with metal housings that ground the cable shielding) or M12 X-coded connectors, which provide an IP67-rated locking interface compatible with RJ45 internally but with a robust threaded outer housing.

Common installation errors with RJ45 include incorrect wiring (mixing T568A and T568B at opposite ends, creating a crossover cable when a straight one was wanted), inadequate twist preservation (untwisting too much of the cable inside the plug, increasing crosstalk), and poor strain relief (which leads to cable damage and intermittent failures over time). For critical installations, factory-terminated patch leads are usually more reliable than field-terminated ones.