The "Template:Commons category" links to a "Category:" name in the Wikimedia Commons repository (edited using a Wikimedia login name). If that category name is misspelled or missing, the link will still appear "blue" even though the link will fail. Check spelling of names carefully.

{{Commons category}} puts link-box with current page's name as the category.
{{Commons category|catnam}} puts link-box connecting title catnam.
{{Commons category|catnam|shownam}} puts link-box showing the title shownam.
{{Commons category |catnam|position=left}} floats link-box to the left side, as option to align box to left-margin.

The two parameters catnam and shownam (1 & 2) are optional, and are intended for cases where the Commons category name is different from the Wikipedia page name. The first parameter is the name of the corresponding category on the Wikimedia Commons, without the "Category:" prefix. If this first parameter is used, then the template will display the Commons category name, which may be confusing to readers. This text can be overridden by the second parameter, where the Wikipedia page name would typically be used.

The parameter "position=" accepts one value, left, that moves the box to the left side, instead of the default right side. More information may be found at {{Side box}}.

For example, on the Polar bear page,

{{Commons category|Ursus maritimus|Polar bears}}

produces a link to Commons:Category:Ursus maritimus displayed as "Polar bears".

If using a large, graphical template produces odd layout problems, like the excessive white space shown on the right of this screenshot, then switch to a different sister template.

N Do not place this template in a section all by itself.

N Do not place this template in a section containing columns.

In articles, this template should normally be placed at the top of the ==External links== section, if one exists, or at the top of the last section on the page, if no external links section exists. On disambiguation pages, this template is usually placed at the top of the page. See Wikipedia:Wikimedia sister projects#Where_to_place_links for more information and alternatives.

In categories, this template should be grouped with other templates at beginning of the category introduction. This avoids unnecessary white space as any text is floated around the template boxes.