I always thought that first variant (both letters written uppercase) is appropriate (maybe because I'm a Windows user), but recently I see more usages of second one (only first letter written uppercase). Which one is more eyes- and mind-friendly?

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    I think it will come down to personal preference - interesting reading here: english.stackexchange.com/questions/108213/… – Midas Mar 16 '16 at 22:18
  • would you use all caps in all use cases if 'ok' is a part of a sentence?? I think it depends on your use case – Igorek Mar 17 '16 at 1:16

Stick with is most common and time-proven. OK (with caps) has been used always. You can see its wikipedia page, is written using both caps.

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    Yes. This is not just a UI issue. The word is “okay” or “OK” not “Ok.” – Simon White Mar 18 '16 at 5:51

If you have space in your UI, maybe consider using a more indicative label like:

'Delete my stuff' 'Sign me up' 'Show me the report'

or the name of the page it takes you to.


OK is the more common one according to ngrams.

It's also worth thinking about how the appearance would affect someone reading aloud. OK is recognisable and forces a break between the letters ("oh kay"), while I've seen people slow down as they remember that Ok is the same thing and isn't "ok" or "och".

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    You forgot to check okay and Okay, too. Both are now more frequent than OK in that Google corpus. – Crissov Mar 17 '16 at 15:17

Whether you use OK or Ok could also be depending on the country/area - in Denmark, e.g. in informal texutual conversations the all-lowercase ok is seen a lot.

That being said, I would go for a button-label which reassures the user of the action which he is performing - as kelbyuk suggests.


Either 'Ok' or 'OK' should be fine, as long as whatever action about to be triggered by the button is crystal clear to the user.

That being said, to me, 'Ok' is cushy whereas 'OK' is serious, so I would use them accordingly based on characteristics of the product.

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