I just got prompted by captcha to enter in the pi symbol. Not really possible on any keyboard I've seen. Could be an issue with the new site.

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    On a Mac with the French Canadian - CSA keyboard layout it's alt+i.
    – zneak
    Commented Sep 5, 2010 at 19:35
  • I just got prompted again to type what seems to be a non Alphanumeric character Commented Sep 5, 2010 at 19:56
  • 1
    Sure it wasn't a n?
    – TheLQ
    Commented Sep 6, 2010 at 3:09
  • reCAPTCHA Tip: Type the shortest word you can read and type, for the other word try to type something as close as possible. You probably could have typed PI or something similar. Even if it's completely unreadable or you are short on time just typing random characters let you through... Commented Sep 9, 2010 at 16:31
  • @zneak, on american mac keyboards it is alt+p. On the PC you hold alt+227 (numpad) I think. Commented Dec 24, 2010 at 20:37

1 Answer 1


I'd recommend reading up on reCAPTCHA.

TLDR: reCAPTCHA is a system that uses captcha strings to parse books that its OCR can't read. You are presented with 2 words- one is a control word that reCAPTCHA knows- the other is a word is hasn't yet determined to sufficient accuracy. So, if you get one word you can read and one you can't, just take your best stab at typing the unreadable one, since it's probably not the control word.

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    Or you could hit the button that gives you a new captcha.
    – bdonlan
    Commented Sep 9, 2010 at 15:24
  • hahaha, so what you're saying then, is that reCAPTCHA is basically crowd-sourcing their text-detection algorithm as an anti-spam service? They get paid twice for the same thing? win. Commented Dec 24, 2010 at 20:35
  • Well, reCAPTCHA is free to use as a CAPTCHA- I don't know whether they charge the people using it for OCR. Actually reading about it now, it looks like Google bought the system and is using it to digitize the NY Times, so I don't think they're charging anyone. Commented Dec 24, 2010 at 21:18

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