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A site as big as stackoverflow must certainly attract a lot of spammers and bots. Hence, I find it strange that they are not using captcha, either to create a new account or to post a new answer as a guest.

Are they using hidden techniques like honeypot or they just expect the community to flag all the spams and delete it?

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  • 2
    Here is a Stack Overflow captcha. Here is a captcha on this very site.
    – Wrzlprmft
    Commented Jan 28, 2016 at 10:20
  • 4
    Related: CAPTCHA frequency is reduced for users who are established/have recently completed a CAPTCHA.
    – Pops
    Commented Jan 28, 2016 at 19:04
  • 1
    The easiest to see that SE uses captcha is to go to Stack Exchange Data Explorer and run the query as anonymous user (without logging in)
    – Andrew T.
    Commented Feb 1, 2016 at 5:06
  • I find it strange that people still expect to see CAPTCHA everywhere. Do you still believe CAPTCHA actually does what you think it does?
    – AviD Mod
    Commented Feb 4, 2016 at 7:35

2 Answers 2

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As stated by Jeff Atwood himself, StackExchange uses several techniques to reduce spam.

  • captcha
  • script detection heuristics and "honeypots"
  • user flagging (spam / offensive / moderator attention)
  • auto-removal of some items based on certain flag thresholds being met
  • active moderator participation throughout the day to look at moderator flagged items

They are also using captchas, which are triggered under some specific conditions. I have to complete one from time to time.

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  • 1 of the conditions of the chapcha is the time it takes between the loading of the page, and the submit of the answer
    – Ferrybig
    Commented Jan 24, 2016 at 17:31
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I just got a CAPTCHA today on stackoverflow while posting an answer, with a message "Please don't take it personally" and an image of 2 humans dressed as robots.

I don't know since when have they started using CAPTCHA, but today was my first instance of using it on Stackoverflow, and I can confirm that it is being used.

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  • 2
    Interesting, never seen one here until now.
    – Rui F Ribeiro
    Commented Jan 22, 2016 at 15:42
  • 4
    Those are not just any two humans en.wikipedia.org/wiki/Flight_of_the_Conchords specifically their song youtube.com/watch?v=2IPAOxrH7Ro
    – corsiKa
    Commented Jan 27, 2016 at 15:24
  • Since a very long time, but with high rep you need to post really fast to trigger it.
    – ThiefMaster
    Commented Feb 4, 2016 at 15:40
  • I saw this years ago
    – Croll
    Commented Feb 4, 2016 at 15:49
  • Robots behind SO noticed that you're posting robots and thought you could be one of them. Too bad you failed test by passing CAPTCHA.
    – Oleg V. Volkov
    Commented Feb 4, 2016 at 17:14

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