Please explain:

  • (1) What leads you to believe the interface is the most commonly used, and
  • (2) Why do you believe that it is an interface.

UPDATE: Leonardo Herrera's answer "The button, and its cousin hyperlink" had been selected as the answer, but a number of users took issue with this answer, so I'm opening the question back up, and have attempted to address the issues raised by adding clarifications to the question itself.

  • Any thoughts about expanding this question to be along the lines of "What are some of the most common user interfaces, and how could they be better?" I think not having to name the 'most' common interface would open up discussion about the various interfaces humanity uses, and how they could be improved. I'd learn a lot from that. Commented Oct 27, 2010 at 16:03
  • @instanceofTom: I just want the most common user interface, not a list of them. In fact, think I'll remove the better part, since I'm really just interested in what the most common interface really is.
    – blunders
    Commented Oct 27, 2010 at 16:11
  • @blunders, fair enough. I may ask my version of the question at a later date because as I said I would learn a lot from it. Commented Oct 27, 2010 at 16:42
  • @instanceofTom: Feel free to ask it today, it's a complete different question, meaning that the answer it's looking for is different. You want a list of answers, I only want one. Plus, I took off the part about making the interface better too.
    – blunders
    Commented Oct 27, 2010 at 17:23
  • The site is a UI site. There is no reason to tag a question as UI. Please do not keep adding that tag to the question. Commented Oct 27, 2010 at 20:08

7 Answers 7


I'm surprised no one has posted this yet:

"The only intuitive user interface is the nipple. Everything else is learned."

I don't know who said it, but I'm pretty sure that's the most common user interface

  • 1
    Thanks for posting, and your answer is one of the VERY reasons I wanted to ask the question... "user interface" is a very limiting set of words for the meaning they cover. Again, thanks!
    – blunders
    Commented Nov 1, 2010 at 21:12
  • 1
    Here's some provenance for the quote (but basically, the origin is unclear): greenend.org.uk/rjk/misc/nipple.html
    – Peter
    Commented Feb 21, 2013 at 17:01
  • Hey Luke Wroblevsky used this example of the nipple interface - look here: (youtu.be/OkeJg92PA4E?t=31m14s) Commented Oct 13, 2016 at 12:04

The button, and its cousin hyperlink.

  • @Leonardo Herrera: +1 Nice answer, question did get me thinking about the difference between a tool, and an interface.
    – blunders
    Commented Oct 24, 2010 at 22:00
  • 2
    A button is not a user interface and neither is a hyperlink. They are elements of a user interface, but alone they are nothing. Commented Oct 24, 2010 at 22:27
  • Please take a look at the OP. The original question is about user interface elements. Commented Oct 25, 2010 at 0:06
  • 1
    @Charles Boyung: Find it really hard to believe that you can't think of an interface that is just one button. Off the top of my head I can think of at least three that are VERY common in the world, or at least the modern world.
    – blunders
    Commented Oct 25, 2010 at 2:41
  • 2
    @blunders: A button without context doesn't mean anything. A button always needs context to make it "useful". For example: a door bell is just a button, put it on a door(frame) and it suddenly becomes useful and part of a user interface. Commented Oct 25, 2010 at 6:18

Well, you really asked more than one question...

Kind of a WAG, but I would say the door knob is the most common user interface in the world.

You probably meant computer interfaces, though. In that case, I'd say the search engine interface.

If you meant most often used, I'd say search engine interface again.

If you meant the most time spent using a particular interface, I'd guess the Facebook News Feed.

  • I was happy with the button answer, but decided to open the question back up since there was a debate over the answer, and wanted to clear it up. As for what "interface" means, that's up to you, really open to any answer that makes sense. And you're point about time spent on Facebook News Feed, are you talking about time spent reading content, or something else?
    – blunders
    Commented Oct 27, 2010 at 18:25
  • Time spent reading, scrolling, commenting, "liking", etc.
    – devuxer
    Commented Oct 27, 2010 at 18:37
  • What about mobile phones? My understanding is that only 7% of the world has access to Facebook, but 60-70% have access to one or more cell phones.
    – blunders
    Commented Oct 27, 2010 at 18:59
  • @blunders, Good point. Or just phones in general.
    – devuxer
    Commented Oct 27, 2010 at 19:30
  • @blunders - but if you are talking about computer interfaces (since you are completely unclear in your question), you couldn't count a cell phone. And cell phones do not all have the same interface. In fact, many aren't even close. Commented Oct 27, 2010 at 20:09

Toilets. Lavatories. Pissoirs.

That's my serious answer. We all use them, and we all have to learn how to use them.

  • There are, as far as I know, two distinct schools of thought as to how toilets should be designed: Western-style sitting vs. Eastern-style squatting. Remind you of anything? ;)

  • Different users use them differently (males vs. females)

  • They can be used differently depending on user requirements (I don't think I need to elaborate)

  • The different types of interface have been designed consistent with the culture of the people who use them (e.g., squatting vs. sitting on something)

It's an interface because it requires some part of the user's body to move and engage with (i.e. touch, or at least get pretty close to) the UI to make the desired thing happen.

Apologies if this comment drags the tone of this excellent post down!


Some oldschool stuff like a standard calculator emulation, a number dialer or a text entry interface like an on-screen keyboard or variations thereof?

What is the most widely used programming API, that would count as a user interface as well, right?

Light switches and faucets seems like other prime candidates as well but then again it's not clear if this is somehow limited to computerized user interfaces ^^ (of where light switches aren't really common yet but I look forward to the chaotic era when I control my bathroom faucet with my smartphone)

  • Thinking the faucet will require authentication using OpenID for any visiting smartphones, er, people. Commented Oct 30, 2010 at 14:23
  • All very interesting answers, and no, I'm not defining what the "user" means, or "interface" means. To me an user could be a number of "things"... for example: human, animal, autonomous system, etc. An "interface" well that becomes much more complex to simplify... :-)
    – blunders
    Commented Oct 30, 2010 at 15:20

That's an easy one.

The most common interface in the world is the command line.

There is no computer, OS, gadget or any other technology with a chipset that can't be accessed from a CLI

  • Very interesting, since I would say that a CLI is a generic term for a type of interface, and agree that it's common to all systems. How often is it used though, and who is the user?
    – blunders
    Commented Oct 30, 2010 at 22:54
  • all OSes have a CLI embedded in their windows systems. So even those "purely" Windows OS still have CLIs. Its not a generic term for an interface though - its the "type stuff out" interface via programming. You could say that Programming apps is a form of CLI interaction too.
    – gbjbaanb
    Commented Dec 24, 2010 at 0:23

The water faucet.
(Or possibly the electric socket - see below)

I read it as about interfaces to complex technical systems - the system providing clean water by means of pipes, pumps, filters etc is certainly complex. And a device to regulate volume per time of water by interaction of typically rotating an element should qualify

In terms of numbers, it's possibly the electric socket along the same lines regarding the system interaction - not sure about the relative number of homes in regions with no electricity lines, but water from a pipe system (as opposed to a well). Also, there is the higher number of sockets that faucets in buildings with both.

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