CAPTCHA is one of the most frustrating security features on the Web. Despite their best efforts to keep nasty bots from creating user accounts, post spam to forums and the like, those funny-looking letters often baffle the most keen-eyed of humans too.

Catcha is a far better (and more fun) solution. It’s based on the theory that only humans will recognise a cat in a series of photos. Displaying three images from Instagram, one of which features a cat, you just select the photo with the feline in it – and voila – you’ve proved you’re human.

Silly and clever in equal measure, Catcha is a hack that developer Syd Lawrence threw together based on an idea by Rich Halliwell. You can try it out on his website, and if you’re a developer yourself you can grab the open source code from Github and develop it further, or add it as a genuine website security feature.

Now, we’re sure that eventually, image recognition scripts could be written to find the cat in the images and beat Catcha, but we’d rather look at cute kittens than obscure letters any day.

➤ Catcha

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