A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.
Questions dealing with moderator actions, pages, abilities or decisions.
Questions about diamond (♦) moderators, their powers, and actions they have taken.
For questions about single users having multiple accounts, known as sock accounts.
For questions about MathOverflow newsletter - possibility of getting an email with top posts.
For discussions and questions on the appropriateness (for the main site) of a question or a certain type of question.
an open standard that allows users to log in to many websites with a single set of third-party credentials.
blocked from asking new questions, or posting new answers.
for problems and suggestions for the privileges gained by reputation on the main site and on meta.
Protected questions have the additional restriction that users with low reputation are not permitted to answer the question.
The undisclosed algorithm through which all new questions are passed to determine if they can be posted on SE.
Questions and discussions on and related to the reputation point system used on the main site.
For questions related to how the site looks, feels and behaves when its responsive design comes into play
For questions about the review queues.
For questions about the various RSS feeds provided by Stack Exchange sites.
for sandbox questions, which allow people to write answers meant for testing of a particular issue, or a draft for a later answer.
For questions about built-in search functionality of this site and about searching this site using external search engines.
the act of casting many successive upvotes or downvotes on the posts of a specific user.
Questions related to the "side bar"; the bar that runs down the right side of the page on Stack Exchange sites.
for discussing platform-wide changes to StackExchange, especially how they impact the MathOverflow site.
Questions about suspected user spam, the spam flag or combating spam as a community
for questions on Meta that relate to a specific answer on MathOverflow. (If a linked answer serves only as an example of a more general issue you want to discuss, this tag should not be u…
For discussions related to some particular question posted (or to be posted) on the main site. Do not use if your intention is to discuss/ask about a general issue, and you merely linked some question…
For questions which focus on a particular user, rather than those discussing general user issues.
Questions about sizes and other quantities of MathOverflow, e.g., number of questions, GB/day transferred, voting statistics, etc.