I was wondering if leaving an active Ethernet port with no plug in it was safe . We have one in our kitchen right next to our face level and I was wondering if leaving it unplugged in the open was safe like does any radiation or infrared laser/light come out of it. Might sound very paranoid but I'm curious.

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    Just to add folks - while there's flaws in the premise of the question, snarky misleading comments are not cool.
    – Journeyman Geek
    Commented Mar 20, 2018 at 10:39
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    The stack exists to build a knowledge base. There should be questions from beginner to extra-advanced expert level. So long the requirements of the help center are met, the level of expertise of the poster is not an issue. Commented Mar 20, 2018 at 12:43
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    What kind of Ethernet port? Is it an RJ45 socket (aka 8P8C, for twisted-pair), or is it a BNC socket (for coaxial cable)? (Not that it makes a difference - it's low-voltage, and RJ45 sockets are usually shuttered, too). Commented Mar 20, 2018 at 13:02
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    There'd actually fibre optic wall sockets too, but its unlikely to be found in a kitchen. If there's protective covers, leaving them on is a good idea to protect the connectors not the people ;p
    – Journeyman Geek
    Commented Mar 20, 2018 at 13:43
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    It would be a good idea to update the question with the type of ethernet port, because if it does happen to be a coax port (not likely in 2018) the answer would be different Commented Mar 20, 2018 at 18:39

4 Answers 4


First: you are safe.

I'm assuming you have the standard plug that looks like this:

ethernet socket

but if it is a wire that plugs into a laptop or desktop computer, the chances are good that it is a standard RJ45 outlet.

In that case, while the device on the other end could supply power to the port,

  1. it probably does not for most home devices / installations, and
  2. the power supplied even in that case is quite limited, and
  3. there is a sophisticated process to detect whether to supply power to the port, and people don't qualify. Also, in this case, there is no laser / radiation at all.

If you are using fibre, you are still safe. A fibre port does output laser light (see here), but it is a "Class 1" laser (see here), so you'll have to try kind of hard to get hurt by it. Plus, if it is fibre, there is absolutely no electrical hazard (fibre doesn't conduct electricity)

It is always reasonable to be interested in safety, and to seek out information to ensure your safety. Keep up the good work.


The question I'd be asking is whether your ethernet is safe from your kitchen? You wouldn't want to splash liquid into the port and cause corrosion of the socket, as then devices plugged in there in the future might not work. To protect the socket, search for a cheap RJ45 Dust Cover on Amazon/Ebay/your local computer store.

Another 'fix' is to take a old ethernet cable with a RJ45 plug on it, and cut it off leaving a inch or so of cable. Plug this into the port to keep dirt/dust out.

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    Every time I have an Ethernet cable fail, I cut off the ends like this and keep them. One reason I like to have some around is to fold a piece of duct tape in half over the cable and write "BAD" on both sides with a permanent marker, to tag jacks and switch ports suspected/known to be bad, so that no one will try to use them. This is another good use for what would otherwise be thrown away. Commented Mar 23, 2018 at 21:22
  • Not jus tthe kitchen - any kind of port that is in reach of smaller children could end up with food wedged in it. Having worked in a high school, I've seen cretins jam metallic foil inside them too.
    – Criggie
    Commented Mar 24, 2018 at 21:30

Completely safe. You can even touch the contacts. Also, even if there is a PoE (Power over Ethernet) injector or supply on the other end, I believe that power is not sent over the wire unless a compatible receiving device is connected at the other end.

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    Isn't PoE low voltage & low current DC anyway, so shouldn't be any more harmful that touching both ends of a AA or D or 9V battery. I wouldn't recommend putting your tongue in there, but should still be a lot safer than the power outlets.
    – Xen2050
    Commented Mar 21, 2018 at 3:03
  • The various PoE standards all use in the region of 48 V and at least 350 mA, that's a pretty good jolt (and enough to be dangerous if applied across the heart). But you're correct, PoE isn't supposed to apply power until negotiations have been made.
    – Hobbes
    Commented Mar 21, 2018 at 19:51
  • What if you lick it?
    – coinbird
    Commented Mar 23, 2018 at 15:36
  • @Hobbes Unless you stab yourself with a fork and then use that fork (still in the wound) to short the socket, said jolt is never going to reach your heart.
    – Christian
    Commented Mar 23, 2018 at 16:11
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    Stick a finger on your left hand in the socket, and your right hand on a nearby grounded object (maybe the kitchen sink). Voila, current path across the heart.
    – Hobbes
    Commented Mar 23, 2018 at 16:33

If it's old enough ethernet - 10BASE5 - then it does need a terminator to stop the waves reflecting at the end and radiating a tiny amount of energy.

The terminators will look like this, from https://en.wikipedia.org/wiki/Electrical_termination enter image description here

If it's a more modern ethernet, then you don't need to terminate. The termination only matters in that it degrades the signal, there is little radiation and nothing that would affect safety - mostly it's there to stop the energy bouncing back into the wire and confusing the electronics.

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    Worth noting that an unterminated 10BASE5 cable is basically a low-powered radio transmitter.
    – Mark
    Commented Mar 20, 2018 at 23:53
  • @Mark from which we should all protect ourselves because of that ever-present danger electromagnetic hypersensitivity...
    – RonJohn
    Commented Mar 21, 2018 at 0:41
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    Huh, from memory, a COAX network (like pictured) doesn't actually work without a terminator, right? Doesn't the terminator connect the inside wire to the outside? Could be misremembering. Commented Mar 22, 2018 at 5:35
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    @SteveBennett it connects it with a resistor to prevent the signal reflecting back into the cable. Whether the network still works depends on how long the cable is (which determines whether the reflection of the signal off the end constructively or destructively interferes, or just combines bits in the packet with ones that were sent a few moments ago), and IIRC to some extent the quality of the network card; the network when I was at university would get slow with lots of packet losses and someone from tech support would come round and check all the terminators. Commented Mar 22, 2018 at 9:33
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    Sorry, @PeteKirkham, but that is incorrect. The terminators are required regardless of the cable length. Without them the cable will not present the correct impedance to the transceivers, so the transceivers will sense "collision" at all times. Even using 75 ohm instead of the standard 50 ohm terminators should cause this problem, though many manufacturers fudged the spec a little so they'd work anyway, as it was a common mistake to use RG59 (75 ohm) instead of RG58 (50 ohm). Commented Mar 23, 2018 at 1:22

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