How facebook extracts the right thumbnail of a link?

Posted by David on Stack Overflow See other posts from Stack Overflow or by David
Published on 2010-05-11T17:15:27Z Indexed on 2010/05/11 17:24 UTC
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php

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regex

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dom

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html-content-extraction

Hi,

I'm wondering how facebook extracts the right picture of the article from a link? they ignore any icons, ads images, or other not related images, & they gives you the right image?

What technique/method they use? because i've tried to extract all images using a php regex but how to find the right one?

Thanks

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