|This page in a nutshell: Hidden text, that is visible only when editing, can be inserted into articles, project pages, and other Wikipedia pages, by surrounding the text as follows: <!-- Hidden text -->|
On Wikipedia, hidden text is text that is visible when editing the source for the page, but not on the saved page. Hidden text is not currently visible to people using the VisualEditor; see bugzilla:49603.
Enter <!-- Comment --> either manually or by clicking the second-to-last link at the bottom of the text box (above “Please note”), and replace the word "Comment" with the hidden text you wish to enter.
- Instructing others how to edit a page that may be difficult to edit
- Providing information to assist other editors in preventing a common mistake. For example if there is a reference which is known to be wrong, it may be appropriate to let other editors know about the error to prevent a likely re-insertion of the error.
- Informing other editors that a section title is linked from a redirect, so that if the title is altered, the redirect can be changed.
- Letting others know of a better article or location within the article to add information on a current event or other hot topic where there is temptation to add it in that location
- Letting others know the location of a template that is included on a page, most commonly an embedded list.
- Reminding others of Wikipedia policies where they have been frequently broken. For example, in many articles, hidden text is necessary to remind editors not to add inappropriate links. On the page Help:Getting started, hidden text is used to let others know not to write their first article on that page.
- Preparing small amounts of information to be added to the article in the future (such as when a known event will occur). Larger amounts of information should be prepared on a subpage of the article's talk page or in user space.
- Hiding a portion of the text that has been temporarily removed while consensus is pending. However, it may be preferable to transfer such text onto a subpage of the article's talk page.
- Asking for others who may edit the page to make certain improvements. There are certain templates that can be used to accomplish this too.
- Outcommenting categories for articles in user pages and user subpages. See: Categorizing user pages
- Cues for bots, such as the <!--BEGIN CFD TEMPLATE--> on categories being discussed at Wikipedia:Categories for discussion
- Asserting ownership of an article
- Telling others not to edit an article, period
- Telling others not to perform certain edits to a page unless there is an existing policy against that edit.
- When it is a mere consensus that a certain edit should not be performed, the hidden text should be worded more softly to suggest to the editor to consult the talk page (or archive page if appropriate) for the current consensus prior to making the edit. Since consensus can change, it is inappropriate to use hidden text to prohibit making a certain edit merely because it would violate an existing consensus.
- Disruptive behavior, such as vandalism, harassment, or threats
- Creating whitespace.