Today, the Pex team is thrilled to announce, a web site that brings code to life. It analyzes small code snippets, and produces a table of interesting input and output values, often uncovering surprising corner cases. The code can be written in C#, Visual Basic, or F#. You do not need to install anything; all the work happens in the cloud. Pex for fun on the web is a radically simplified version of the fully featured Pex Power Tool for Visual Studio.

Go to, which comes with a set of code puzzles. Then click on the “Ask Pex!” button to get the answer yourself. Share your puzzles with your friends.


Comments (5)

  1. tobi says:

    How nice! (The first puzzle says "seconds" in the comment instead of minutes).

  2. Thanks for reporting the "seconds" in the comment for the Y2K puzzle, which should read "minutes". This will be fixed when we roll out the next version of

    Btw: There is no 'first' puzzle. Every time you visit the website, it starts with a random puzzle.

  3. Great idea, I love it.

    Is there are way for the community to submit challenges to Pex, challenges that others would see? I think the community could come up with some interesting challenges.

  4. Hi Judah, thanks for your feedback. There is currently no platform that we provide for sharing puzles with other people. This is definitely missing, and we are looking into creating such a platform. Note that you can already create Permalinks for particular puzzles (the last icon in the 'Share' section under the program text box), which you can share via your own community platforms. I'll create a thread on our MSDN forum where people can share puzzles for now.

  5. Balaji says:

    Hi Nikolait, PEX is very innovative and useful for our team. I've MSDN subscription and I'm seeing exciting results for my web service projects. we write commercial applications for our company

    I've a question on licensing: My team (almost 15 Developers) has VSTS 2010 Professional Edition and they do not have MSDN Subscription. but we want to have Pex for every developer

    My company is not interested in paying MSDN Subscription for everyone and every year for just PEX.

    Is there any options I do have? I can just purchase PEX for 15 developers. not the MSDN subscription??

    Please answer my question. We need this information as soon as possible

Skip to main content