Possible Duplicates:
How does the automatic subjective filter work?
What algorithm does StackOverflow use to determine if a question may be subjective?

I know this is a discussion of the site itself so might be more fit for Meta Stack Overflow, but it is also a programming discussion.

I'm wondering what the algorithm for SO's question validation tool is. (Meaning the warning that a question might be closed for this or that reason).

Edit: no, no, I don't mean how questions become closed. What I mean is the following:

When you open a new question, and you are typing in the question title, sometimes a red line of words will pop up reading "The question you're asking appears subjective and is likely to be closed."

  • 1
    It's not an algorithm - anyone with 3,000+ rep can vote to close a question. It takes 5 votes to close a question: stackoverflow.com/faq
    – OMG Ponies
    Aug 6, 2010 at 0:58
  • 1
    I upvoted your question because it's brave :) It's a good question, but you could just as easily asked about general question validation tools SUCH AS that on StackOverflow. That might result in pointers to generalized textual algorithms. I wouldn't mind hearing the answer in any case.
    – mettadore
    Aug 6, 2010 at 0:59

2 Answers 2


IIRC, it's not very sophisticated. It just looks for subjective words like "best" or "most". And I think it all happens in javascript, so you can likely view the code yourself.


Well this is probably a ridiculous answer, but whatever. I have no knowledge of how SO does it, but my guess is it's either something simple like a dictionary of subjective-sounding words that cause the flag, or it could be something crazy complicated like something Google would do where it builds an index of all previously-closed subjective questions, and compares the question to that index; so for example if there are words that tend to be used frequently in subjective questions, they might cause the flag. So basically the same as my first idea, except with an adaptive dictionary based on statistics gleaned from actually-closed questions. :)

  • -1 since a correct answer is known and this is a shot in the dark; on second thought, removing the downvote because this has already been closed as a dupe
    – Pops
    Aug 6, 2010 at 13:31

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