Finally, a captcha that works for humans

Captchas are simultaneously the greatest and worst things ever invented.

CAPTCHA is short for Completely Automated Public Turing Test To Tell Computers and Humans Apart. The term was coined in 2000 at Carnegie Mellon University,where these little challenges you face when you try to do something on a web site were born.

The idea is to build a test that proves you’re a human, not a machine, by generating and grading tests that humans can pass but current computer programs cannot.

That’s essential, in a world where bots (no relation) are trying to take over everything on the Internet that involves money.

The trouble is, captchas are frequently too hard for mere mortals, with text so distorted that even the most human of humans can’t pass.

Here, for example, is a Ticketmaster captcha that I saw just seconds ago:


I can kinda sorta make that out, but it’s not easy. And that’s one of the easier captchas I’ve seen lately.

It’s gotten to the point where I frequently have to refresh the captcha three or four times before I get to one that I can actually read.

Which is why I was so glad to see this program from Microsoft Research:


Asirra is a human interactive proof that asks users to identify photos of cats and dogs. It’s powered by over three million photos from our unique partnership with

Asirra (Animal Species Image Recognition for Restricting Access) … works by asking users to identify photographs of cats and dogs. This task is difficult for computers, but our user studies have shown that people can accomplish it quickly and accurately. Many even think it’s fun!

Here’s what a typical test looks like:


I had no trouble with this test, in stark comparison to text captchas.

Which do you prefer?

10 thoughts on “Finally, a captcha that works for humans

  1. Ed:

    “(no relation)” — love it!!

    In this particular instance, as presented here, I actually found the text CAPTCHA easier to do; the photographs are sized too small — for me — to make out that they even contain animals of any species. I’d like to see this in actual practice before passing final judgment on which I prefer.

    — Timothy J. McGowan

    1. Timothy, if you use the actual captcha example, the photos expand as you mouse over them, so it’s easy to see what they are,

      Ben, I inadvertently left out the link to the original article when I posted this last night. I apologize and have fixed that now. I’m not sure who you’re referring to when you say “the guy that created it,” though. The MS Research team cites at least three sources who did similar work on which they have built.

  2. I’ve seen the Microsoft solution out in the wild before. I like it much better. Captcha seems to be getting worse every year.

  3. Why create this article and not even mention the guy that created it? Give credit where credit is due.

  4. I too found the text easier, as did the general public (in my case). I found the cat based version a few months ago, and tried it for a while on one web site. Got more than double the complaints about needing to do this. I found a number of pictures in it where you really couldn’t tell if it was a dog or cat! Plus, I agree with Tim in that the pics are just too small. If they’d fix that, and be more subjective about the pics then mabye. I’m still shocked that the complaint rate went up on the change.

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