For a single use footnote, the label is followed by a caret (^) that is a backlink to the matching footnote marker. For example:
If a named footnote is used in the text multiple times, then the footnote has multiple backlinks shown as letters:

To create the footnote marker, determine the point in the page content where the marker is desired and enter the markup with the citation or note inside the <ref>...</ref> tags. For example:

The content inside the <ref>...</ref> will show in the reference list. The ref tags can be added anywhere a citation or note is needed. There must be content inside the tags, else an error will show.

Ref tags should follow any punctuation (usually a period), not precede it; see WP:REFPUNC. There should be no space between the punctuation and the tag:

Single apostrophes do not need to be encoded; however, unencoded multiples will be parsed as italic or bold markup. Single curly closing braces also do not need to be encoded; however, an unencoded pair will be parsed as the double closing braces for the template transclusion.

You can cite the same source more than once on a page by using named footnotes. The syntax to define a named footnote is:

The actual name used can be almost anything, but it is recommended that it have a connection to the citation or note. A common practice is to use the author-year or publisher-year for the reference name. This helps editors remember the name, by associating it with the information that is visible to the reader.

Note that the footnote labels are incremented in the order they are used, and that they use the same label when reused, thus the labels can seem out of order:

Care should be taken when deleting references to avoid creating a cite error. See Avoiding common mistakes.

By setting the width in em, the number of columns will automatically be adjusted to the width of the display. It should be used only when necessary, as the template has built-in auto-formatting capabilities providing a useful display in most scenarios by itself.

The number of columns to use is up to the editor, but some major practices include:

Some or all of the footnotes can also be defined within the reference section/list, and invoked in the page content. This keeps those citations in one central location for easier maintenance and avoids cluttering the text. This is purely a source code change – the actual display of the citation in the text to a reader is unaffected. For a more detailed evaluation of this method, see WP:LDRHOW. The syntax is:

The footnote markers are included as usual for a named footnote. For example:

The references will be numbered, and appear in the output, in the order that they are first referred to in the content, regardless of their order within the list. All references in reference list must be referenced in the content, otherwise an error message will be shown.

Note that when you use the visual editor, you will not be able to add, remove, or change list-defined references.

Sometimes it is useful to group the footnotes into separate lists, for example to separate explanatory notes from references, or to list references for tables, image captions, infoboxes and navboxes. The sequence of footnote labels is independent in each group.

The footnote marker group name must be enclosed in quotes if the group name includes a space, else a cite error will occur, otherwise quotes are optional.

Note that the footnote labels in the reference list show only the numbers and not the group name.

These predefined note and citation groups have templates that make the wikitext markup simpler. These templates also allow a standard reference to be inserted, so that an explanatory note can have a reference, or citations can be nested.

In these examples, the footnote labels match between the footnote marker and the reference list:

Note: With named references you only need to add the details once. For each use after the first you just need to re-use the reference name. Doing this will not cause the inline superscript to display a custom name.

A page with <ref> tags but no reference list markup used to display an error, except on talk and user pages. In recent versions of Wikipedia, the error no longer appears; instead an automatically generated reference list (AGRL) is displayed at the bottom of the page.

Compared to the reference lists on properly formatted pages, an AGRL can be confusing to both readers and editors. But it is easily corrected by adding reference list markup such as the following. Add it at the position where the reference list would normally appear.

Suppose you would like to cite one book, but different facts appear on different pages. You would like to cite the book again and again, but point each fact to the proper page. Suppose one fact is on page 8, a different fact on page 12, a third fact on page 18, a fourth fact on page 241. You could put a line in the "pages" parameter saying "see pages 8, 12, 18, 241" but a fact-checker might have to check all of them before figuring out the right one. Or, you could duplicate the entire citation for the book in each instance, but that would be redundant.

Using the citation toolbar to insert additional references to the first source.

You can use the citation toolbar to name references. When you first create a reference, you can enter a value in the "Ref name" box. When you want to reuse this reference, click the "Named references" button on the citation toolbar and choose which reference you would like to insert.