Computerhelp4all logo Articles AboutTopicsQuizzesComputer Questions & AnswersComputer Terms & DefinitionsActivitiesContact

What Is RJ45?

What Is RJ45

Date First Published: 27th April 2022

Topic: Computer Networking

Subtopic: Network Hardware

Article Type: Computer Terms & Definitions

Difficulty: Medium

Difficulty Level: 5/10


Learn more about what RJ45 is in this article.

Short for registered jack 45, RJ45, sometimes spelt RJ-45, is the connector used in Ethernet cables that can be seen at the end of the physical cable. The jack in Ethernet cables is slightly wider than telephone jacks and the '45' in RJ45 refers to the interface standard.

RJ45 connectors are often confused with the 8P8C standard, since they both look very similar. However, 8P8C has certain properties in regard to signal loss. This is because the cabling is always made up of twisted pairs, which is a noise-cancelling technology.

Note: Info Icon

RJ45 connectors usually make a connection between the network card of a computer and the network device, such as the router or switch.


RJ45 connectors consist of 8 pins and 8 separate wires of different colours. 4 of the 8 wires are solid colours and the others are striped. The individual wires are spaced 1 mm apart. There are also two ways that RJ45 connectors can be wired, known as T-568A and T-568B.

Even though most devices are compatible with the T-568A wiring scheme, the T-56EB wiring scheme is much more common. Direct connections with no routers, hubs, or switches use crossover Ethernet cables, where there is a T-568A connector on one end and a T-568B connector on the other end.


  • Is there anything that you disagree with on this page?
  • Are there any spelling, grammatical, or punctuation errors on this page?
  • Are there any broken links or design errors on this page?

If so, it is important that you tell me as soon as possible on this page.