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Term Reference Tree provides an expandable tree widget for the Taxonomy Term
Reference field in Backdrop. This widget is intended to serve as a replacement
for Backdrop's core Taxonomy Term Reference widget, which is a flat list of
radio buttons or checkboxes and not necessarily fit for medium to large taxonomy

This widget has the following features:

  • Expand/minimize buttons
  • Fully themeable
  • Filter and sort available options with a View
  • The ability to start with the tree either minimized or maximized
  • If you limit the number of selectable options, client-side Javascript limits
    the number of terms that can be selected by disabling the other remaining
    options when the limit has been reached (this is enforced on the server side
  • For large trees, this widget now optionally keeps a list of selected items
    below the tree.
  • You can use tokens to alter the widget label (good for adding icons, turning
    the options into links, etc).

This module comes with a display formatter with the following features:

  • Display taxonomy terms as a nested list by hierarchy.
  • Displayed terms can be altered with tokens or themed using a custom theme


Install this module using the official Backdrop CMS instructions.

  1. Go to the Manage Fields tab of any fieldable entity, such as a content type,
    taxonomy term, or user.
  2. Add a new field with a type of Term Reference.
  3. In the widget select box, select Term reference tree as the Widget Type.

Note that you can also change any Term Reference field to use the Term Reference
Tree widget, by editing that field and selecting Term Reference Tree on that
field's Widget Type tab.

If you want to filter by a view, make sure the view includes the taxonomy term
ID, and that the items per page is set to unlimited, as the widget will only
display the items from the first page of results.

This module is also perfectly good for flat lists, particularly if you want to
filter them by a view or limit the number of selectable options with JavaScript.
It's a good idea to turn on the "leaves only" option in this case, as it will
make it look nicer.

Differences from Drupal 7

The Backdrop version of this module has some additional classes applied to the
li elements of the rendered tree to give more flexibility in theming:

  • li elements have class has-children or no-children, as applicable.


Bugs and feature requests should be reported in the Issue Queue.

Current Maintainers



This project is GPL v2 software.
See the LICENSE.txt file in this directory for complete text.