What does it mean if a question is "closed"?

Why are some questions closed?

Questions that need additional work or that are not a good fit for this site may be closed by experienced community members. Closed questions cannot be answered, but can be edited to make them eligible for reopening. If your question is closed, you will receive private feedback on the reason why it was closed.

Any closed question that receives one reopen vote by a user with sufficient reputation is automatically added to a reopen queue for community review. In addition, any question with significant edits that address the close reason(s) gets added to the reopen queue. If enough community members agree, the question will be reopened and can accept answers.

These are the categories of questions that may be closed by community members with the close/reopen votes privilege. The quoted text below reflects what is shown to close voters when voting to close a question:

  • Duplicate of... - The fundamental goal of closing duplicate questions is to help people find the right answer by getting all of those answers in one place. There’s more information in our duplicate questions help center article.

    This question has been asked before and already has an answer.

  • Off-topic because... - Each community decides which specific topics are and are not allowed on their site. You can see this list of off-topic subjects for this site by viewing this help center article.

    This question does not appear to be about programming within the scope defined in the help center.

    If you believe the question can be reworded to fit within the scope, consider editing the question or leaving comments for improvement.

  • Needs details or clarity - Sometimes we need more information in order to help solve your problem.

    Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question.

    Edit your post to be more specific about what you're looking for, and be sure to address any concerns that other users brought up in the comments.

  • Needs more focus - If your question has many valid answers (but no way to determine which - if any - are correct), then it probably needs to be more focused to be successful in our format.

    Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question.

    This can often be fixed by breaking the question into multiple questions or focusing on a specific part of the problem.

  • Opinion-based - Discussions focused on diverse opinions can be great, but they just don't fit our format well.

    Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than on facts, references, or specific expertise.

    It’s often possible to rewrite opinion-based questions to focus on a more fact-based line of questioning. If you see a way to do this, consider editing the question.

Who can close questions?

Users with 3000 reputation can cast up to 24 close votes per day. When a question reaches 5 close votes, it is marked as being Closed, and will no longer accept answers. Users with the same privilege may also vote to reopen questions the same way. Each user may only vote to close and reopen a given question once. (For example, if you vote to close a question that is closed and then later reopened, you cannot vote to close it again.)

Moderators may close or reopen any question with a single vote without any of the restrictions mentioned above.

For more about reopening questions, see "What if I disagree with the closure of a question? How can I reopen a closed question?"