Taxonomy dupecheck module prevents Drupal administrators from adding duplicate taxonomy vocabularies and/or terms. It's helpful when entering large amounts of terms or vocabularies in situations where each value must be unique. This saves time by preventing administrators from having to enforce a unique value policy through later cleanup of duplicate terms.

The module provides a configuration screen allowing administrators to choose which should be unique: taxonomy terms, vocabularies or both. It defaults to case-insensitive comparisons, with an option to change to case-sensitive. Both stored and input terms/vocabularies are trimmed before comparison to handle cases such as 'foo ' and 'foo'. Based on the settings, the user will see an error message when adding a duplicate value.

Caveat: due to the inability of hook_taxonomy_term_presave() to stop the saving process, this only works in the taxonomy term and vocabulary forms. If you want to prevent duplicates through other entry points, this module will not prevent that. If someone knows a way around that I will happily add that in, as that was the original plan.

Installation

Please see current README.txt.
Make sure to grant the "administer taxonomy" permission.
Configure settings at Admin > Modules > Taxonomy dupecheck > Configuration

Taxonomy dupecheck

Issues