Wikipedia:Spoiler

Wikipedia occasionally uses spoiler tags to mark off certain significant plot details ("spoilers") in articles about fictional works. This is an exception to the style guideline no disclaimers in articles. However, since Wikipedia is a user-created and user-edited encyclopedia, there is never a guarantee that any given article will be tagged for spoilers; caveat lector!

Usage
To insert a spoiler tag, enter the text   before the passage to be marked off, and close the tag with   . For further details on syntax, see the template page. Since the spoiler tag exists, it should never be necessary to add homebrew spoiler protection to articles.

Spoiler tags should only be used when there is a reasonable expectation that narrative suspense is a significant element in the appreciation of the work. Often they won't be necessary at all if the article is well-structured. As with all Wikipedia edits, spoiler tags should be guided by consensus editing; if you are in doubt, discuss the matter first on the article's talk page.

Below are some questions to ask before adding, deleting, or moving a spoiler tag:

Is it widely known?

 * If a plot point has made significant penetration into popular culture, it is often no longer necessary to mark it off with spoiler tags. The existence of well-known parodies and other unconnected pop-culture references can be cited as evidence for "significant penetration".
 * The older a work is, the more likely its plot details are to be widely known. After a certain point, the age of a work usually makes spoiler tags completely unnecessary — nobody needs to be warned about the ultimate fate of Hamlet — but age alone is not always sufficient for lesser-known works. (A newly discovered Shakespeare play could conceivably have a spoiler warning for a while.)
 * A very new work may be better served by the current fiction tag, which duplicates and adds to the information in the spoiler tag. A current fiction tag should be added to the beginning of the article, whereas spoiler tags are used within an article to mark off particular passages.

Are spoilers implied by the section title?

 * A section header such as "Plot Summary," "Detailed Summary," or "Synopsis" can be considered a de facto spoiler notice — a synopsis will necessarily describe the entire plot, so there's usually no need to repeat the warning.
 * A section header such as "Plot" or "Overview" can be ambiguous as to the presence of detailed spoilers, particularly for a newcomer to Wikipedia. If that section contains significant spoilers, consider changing the header to something clearer. Sometimes, a separate "Overview" paragraph may be appropriate (or may be included in the lede), containing a "back-of-the-book" style overview of the story, in which case significant plot details should be moved to a more clearly labeled section.
 * If separate plot-related sections are not appropriate for the article, you may consider merging them into a single section: an opening paragraph that offers an overview of the plot, then a detailed passage marked off with spoiler tags.
 * If a plot detail that arises in an unexpected place — a "Cast of Characters" or "Setting" section, for instance — consider moving that detail to a more appropriate section, or changing the section title. Alternatively, the unexpected plot detail may be marked off with spoiler tags.  (Remember that those who are likely to be surprised are those who are unfamiliar with the work, so they may not know where to expect spoilers!)
 * In a work that is uncommonly reliant on the impact of a plot twist or surprise ending — a murder mystery, for instance — a spoiler tag may be appropriate even within a properly labeled "Synopsis" section. These should be sourced when possible (e.g., by citing a professional reviewer who describes the impact of the surprise).

Should this article contain spoilers?

 * Yes! It is almost never acceptable to delete information from an article because it constitutes a spoiler. Consider moving it or marking it off with spoiler tags — that's why they exist, after all!
 * Spoiler tags should not be used in articles on non-fictional subjects. If explicit spoilers are mentioned in non-fiction articles (e.g. articles on authors, actors, real-life locations in which fictional texts are set, or literary concepts like climax), consider whether that plot detail improves the encyclopedic quality of the article. It may be better to remove the example.