Automatic conversion of wikitext can be divided into three categories:

• The result of the conversion is shown when pressing "Show changes". The rendering is shown with "Show preview". The conversion does not display in the edit box (save and press Edit again to see the result in the wikitext there):
  • ~~~~ produces Username 10:58, 20 Jul 2004 (UTC). This is a piped link to your user page and the UTC time and date. This is referred to as signing and is used on talk pages. The date format is based on the preference of the user who signed, not your time/date preference.
    
    An alternative label for the link (nickname) can be set in the User Data section of your preferences. The feature can even be used to create an additional link to your user talk page, etc. See also Wikipedia:Sign your posts on talk pages and Help:Editing#Links, URLs.
    • Additionally:
      • ~~~ gives username only e.g. Patrick
      • ~~~~~ gives date only e.g. 08:41, 25 Jul 2004 (UTC)
  • subst, see Help:Substitution
  • see Piped link

The code ~<includeonly>~</includeonly>~~ will be displayed as ~~~ when the template is not included, ~~~~ when the template is included, and it will be expanded as the active user when the template is subst'd.

• The result will not be displayed at all:
  • Redirects will show a page containing a redirect link, not the page being redirected to. Everything below the redirect (not extra text on the same line) will be automatically blanked (though it will still be there in the wikitext)

• The result will be displayed in the preview and in the edit box:
  • in the Esperanto Wikipedia, a character like Ŝ is automatically converted into the alternative notation Sx, because in some browsers it may not display in the edit box, even if it displays in the webpage (and Sx, whether resulting from this conversion or just typed, is rendered as Ŝ)

Note: the wikitext only shows the result, not how it was entered, which means that when testing these features, one has to remember or record what one has entered.