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Difference Between RJ45 and CAT5

RJ45 vs CAT5

When it comes to wired networking, RJ45 and CAT5 are two of the most common terms being thrown around. What most people don’t know is that although these terms are often used to refer to the same cables, they are not the same. RJ45 is the electrical interconnection standard that defines the connector and how the wires are arranged at the end of the cable while CAT5 is a standard regarding Ethernet cables.

RJ45, with the acronym RJ standing for registered jack, started out as an interconnection standard intended for telephones and looks pretty much like a bigger version of the RJ11 used in our landlines. It never saw widespread use in telephony but has flourished in computer networking where it became the standard for wired networking. Some homes do have RJ45 wall outlets but these are often used to connect VoIP phones rather than for connecting a laptop.

CAT5, a common contraction for category 5, is a classification of cables that are used for Ethernet networks. A single CAT5 cable contains four twisted pairs of color coded cables. The twisting of the wires reduces the amount of crosstalk and cancels out EMI. CAT5 cables rely on the twisting for noise reduction and are not shielded. This can be problematic in some areas where electrical noise is great. CAT5, or to be more accurate CAT5e, cables are currently the ones that are being used in most networks nowadays. It provides adequate bandwidth for the 100mbps connections of LAN cards. Due to ever increasing network speeds and the need to be prepared for future technologies, it is slowly being replaced by CAT6 cables though as CAT5 is inadequate for gigabit speeds.

So, to sum it all up, RJ45 and CAT5 are two parts of wired networking that are non-competing. RJ45 dictates how the cables are wired while CAT5 dictates the maximum speed you can attain with the cables used. CAT5 is easily replaceable and that is what’s basically happening in certain parts of the world. RJ45 is more difficult to replace as that is what’s being used by hardware manufacturers around the world; and, there is really no reason to replace RJ45.


1.RJ45 is the electrical interconnection standard while CAT5 is the cable standard
2.RJ45 dictates with what you can use the cable for while CAT5 determines how large a bandwidth you have

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  1. I’m sorry, but this didn’t help at all.

    Maybe using more common terms or ways to explain it.

    • What didnt you understand “…RJ45 dictates how the cables are wired while CAT5 dictates the maximum speed you can attain with the cables used…”

      • Are they wired the same. Is a RJ45 wired the same as a CAT5?

        • Mark and Charlie,
          The thrust of the article is that RJ45 refers to the sockets at either end of the cable. CAT or CAT6 refers to the cable that connects the two sockets.

          A CAT 5 or CAT 6 cable will operate at speeds in accordance with the electrical standard upon which they are based (CAT5=1GBs, CAT6=10GBs).

          An RJ45 connector will be placed at either end of your chosen cable that will plug into your internet modem and also your computer.


  2. RJ45= connector
    CAT5 = wire

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