Built-in WordPress Taxonomy & Post Type  Reference

Below is a list of WordPress built in taxonomy names and built-in post type names. Never name your custom taxonomies and post types with one these to avoid collisions.

Taxonomies

• category — Categories (Posts)
• post_tag — Tags (Posts)
• nav_menu — Menu items (Appearance > Menus)
• post_format — Post formats

Post Types

• post — Posts
• page — Pages
• attachment — Media attachments
• revision — Post revisions
• nav_menu_item — Menu items (Appearance > Menus)

This information can also be found in the WordPress codex, but it’s rather buried and difficult to find. Hopefully this helps anyone looking for a quick reference to the names of WordPress built in taxonomies.