[HN Gopher] Why do Macs ask you to press random keys when connec...
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Why do Macs ask you to press random keys when connecting a new
keyboard?
Author : zdw
Score : 25 points
Date : 2026-04-06 16:40 UTC (2 days ago)
(HTM) web link (unsung.aresluna.org)
(TXT) w3m dump (unsung.aresluna.org)
| alsetmusic wrote:
| Mapping to ensure that it has the correct layout applied.
| Our_Benefactors wrote:
| Yes, but this doesn't answer why I only have to do this on Mac
| and not windows/linux, where I have literally never run into an
| issue as a result of not doing it.
| QuercusMax wrote:
| I assume for some nonzero percentage of folks it _doesn 't_
| work right and they have to manually go and set their
| keyboard layout.
|
| Of course, when you're setting up your OS initially, it will
| ask you questions about language and keyboard layout. I
| suspect most people don't switch keyboards after install, and
| of those who do, the most common case is another keyboard
| with a compatible layout.
| HPsquared wrote:
| I assume you have a standard US keyboard.
| jasonjayr wrote:
| Most non-Apple branded keyboards are _NOT_ tested with mac;
| so it doesn 't trust any electronic tags/labels, nor does it
| keep a database. Easiest thing to make it work 100% without
| asking the user to identify their layout, is to press random
| keys so the mac knows where things are mapped.
| masfuerte wrote:
| Windows and Linux both ask for your language and locale
| during setup and default to the typical matching keyboard.
| I'm nearly sure Debian also asks you to confirm the keyboard
| it picked, but it's always the right one so I just hit enter.
| thebruce87m wrote:
| Do you live in a country where the default always maps
| correctly? My UK keyboards will always have specific keys
| wrong.
| dlcarrier wrote:
| If you're using a US English keyboard layout, it's the
| default and you won't have to deal with changing it.
|
| The most likely reason it would be a problem then would be
| that some Raspberry Pi images have defaulted to British
| English keyboard layouts. Otherwise you may be sailing
| through life unburdened by what can be a major pain to anyone
| anywhere else in the world, like a resident of Arizona
| wondering why the rest of the world keeps messing with their
| clocks.
| altairprime wrote:
| See also the layout identifier manual-elsif/elsif/elsif workflow
| here, last updated November 2023:
|
| https://support.apple.com/en-us/102743
| throwaway27448 wrote:
| Random [?] arbitrary
| chimeracoder wrote:
| > Random [?] arbitrary
|
| Sure, though if you're looking to be pedantic, the keys they're
| asking you to press are neither random _nor_ arbitrary
| throwaway27448 wrote:
| How are they not arbitrary? Apple tells you a specific key to
| press, which is a choice. It is by definition arbitrary.
|
| Edit: perhaps you're making the case that the user doesn't
| choose which key. This is true--but the important point is
| that one of the two parties _did_ choose the specific key to
| press.
|
| Edit2: For those downvoting, perhaps you could articulate
| why.
| lgas wrote:
| Arbitrary and random are basically the same in this
| context. The person you're replying to is pointing out they
| are specific keys for specific reasons because those
| specific keys can be used to figure out which kind of
| keyboard it is, they are not random or arbitrary, they are
| chosen with a specific reason in mind. If they were really
| chosen arbitrarily, they would not be able to accomplish
| the goal.
| toast0 wrote:
| My impression is that Apple's choice of keys was
| constrained.
|
| The American Heritage(r) Dictionary of the English
| Language, 5th Edition defines arbitrary as
|
| > Determined by chance, whim, or impulse, and not by
| necessity, reason, or principle.
|
| But the choices seem to be based on reason or principle.
| dylan604 wrote:
| they are not random requests. they are keys known to have
| different locations depending on the locale. by seeing what
| the values sent when the requested key is pressed, they
| know how to map the inputs from the keyboard.
|
| that definitely does not sound arbitrary to me.
| emeraldd wrote:
| Honestly, the mac approach makes much more sense from an ease of
| use perspective for non-experts. On other platforms, you have to
| know the layout to choose and hope things work until you do or
| have a second keyboard that's close enough tl the default to get
| by. On Mac, it just figures it out based on the information you
| tell it when the keyboard is connected. Much less error prone in
| the majority of cases.
| srean wrote:
| Ah! Thanks for the stimulation. That's an interesting problem
| that I had not thought of before. In fact a few related problems.
|
| What's the minimum set of requested key presses that will
| uniquely identify a keyboard layout from a set of known types.
|
| Given a budget of k key strokes what's the most informative
| subset that will reduce the ambiguity about layout.
|
| Given the measurement from the requested key strokes find the
| posterior over the set of known keyboard layouts.
|
| Given that the user is typing some free form text in his language
| how soon can one nail the layout when the user's language, the
| layout and the text are unknown. Will make a good practice
| exercise for hobbyist codebreaking.
| dirasieb wrote:
| they don't ask you to press random keys
| ginko wrote:
| I guess the moment has passed by now but I wish there were a USB
| HID protocol for keyboards to identify their layout, or even
| better yet make the keyboard protocol layout agnostic so that
| keyboards send the high-level unicode character / modifier
| instead of a physical key code.
| weinzierl wrote:
| I think every OS should ask you to press a freshly generated
| sequence of keys when connecting a keyboard to prevent BadUSB
| attacks. Does any system do this?
| avidiax wrote:
| That would break credit card readers, barcode scanners, and
| special purpose keyboards (like video workstations).
|
| I suppose you could rely on a binary code, where the user is
| instructed to press any two keys to repeat the code, or if
| there is only one key (or it's a barcode scanner), to enter the
| same input multiple times, separated by long and short pauses.
|
| Still seems like it would be difficult for the average user.
| vinni2 wrote:
| Why does it sometimes ask when connecting a HDMI projector?
| leejoramo wrote:
| Many projectors include remotes that allow you to control a
| slide presentation. These remotes send the default keystrokes
| that Microsoft PowerPoint knows (and which other presentation
| software copied) So when you connect a projector the OS often
| sees a keyboard and mouse. This triggers macOS's keyboard
| recognition tool. Old VGA projectors had separate
| keyboard/mouse ports. I assume HDMI has a USB channel?
| tomasphan wrote:
| Apple has to make it annoying to use a non-Apple device with your
| Apple device. That sort of friction probably nets them 2% in
| keyboard sales per year.
| daft_pink wrote:
| Thanks I'm always worried. I do the wrong thing when that thing
| pops up for my mouse.
| ch_123 wrote:
| In addition to the three physical keyboard layouts in this post,
| there's a fourth one which has an extra key on both the right and
| the left side of the keyboard. An example is the Brazilian
| Portuguese layout Model M (pic:
| https://www.clickykeyboards.com/wp-content/uploads/2023/03/I...).
| The Apple test would be able to identify it, although I've never
| tried it in practice. I don't think the modern Brazilian Apple
| keyboard uses this arrangement.
| hennell wrote:
| I feel like a UK windows keyboard and a Mac has some oddities
| like this. I've got a zsa split keyboard and still haven't worked
| out how to have punctuation the same in Mac and windows. @ and "
| are always flipped and I had to add additional buttons to ensure
| I have a | and ~ keys because who knows where the Mac thinks they
| are.
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