Hierarchical vs Non-Hierarchical Taxonomies Explained

Customization

December 18, 2025

Hierarchical vs Non-Hierarchical Taxonomies Explained (WordPress)

Taxonomies are one of WordPress’s most important content-structuring tools. However, many site owners struggle with a basic question:

Should I use a hierarchical or non-hierarchical taxonomy?

This article explains the difference in clear terms, shows when to use each type, and helps you choose the right structure for SEO, usability, and long-term maintenance.

What Is a Taxonomy in WordPress?

A taxonomy is a way to group content. WordPress ships with two default taxonomies:

Categories → hierarchical
Tags → non-hierarchical

You can also create custom taxonomies for Custom Post Types (CPTs).

Hierarchical Taxonomies (Like Categories)

A hierarchical taxonomy allows parent–child relationships between terms.

Example structure:

Tutorials
- Beginner
- Advanced

Key Characteristics

Terms can have parents and children
Displayed as checkboxes in the admin UI
Ideal for structured, broad-to-narrow classification

Common Use Cases

Blog categories
Product categories
Documentation sections
Location-based structures (Country → City)

Non-Hierarchical Taxonomies (Like Tags)

A non-hierarchical taxonomy has no parent–child relationship. Each term exists independently.

Example structure:

SEO
Performance
Security
Accessibility

Key Characteristics

Flat structure (no nesting)
Displayed as a tag-style input field
Designed for descriptive labels, not structure

Common Use Cases

Topics and concepts
Features or attributes
Keywords for filtering/search
Loose cross-cutting labels

Admin UI Differences (Why This Matters)

The taxonomy type directly affects how editors interact with content.

Hierarchical UI

Checkbox list
Clear visual structure
Harder to accidentally create duplicates

Non-Hierarchical UI

Free-text input
Autocomplete suggestions
Easier to create similar or duplicate terms

Tip: If you have non-technical editors, hierarchical taxonomies are often safer.

SEO Implications

Both taxonomy types can be SEO-friendly — if used correctly.

Hierarchical Taxonomies and SEO

Create clear content silos
Improve internal linking structure
Often used as primary archive pages

Non-Hierarchical Taxonomies and SEO

Can explode into many thin archive pages
Require careful indexing control
Best used sparingly and intentionally

Best practice: Index hierarchical taxonomies by default. Be selective with non-hierarchical taxonomy archives.

When to Use Hierarchical Taxonomies

You need clear parent–child relationships
Terms represent sections of your site
Content naturally fits into a tree structure
You want predictable navigation and breadcrumbs

Examples:

Documentation → Guides → API
Products → Laptops → Gaming
Services → Consulting → WordPress

When to Use Non-Hierarchical Taxonomies

You’re labeling content, not structuring it
Terms overlap across multiple sections
You want flexible filtering options

Examples:

“Beginner-friendly”
“No plugin”
“Core Web Vitals”

Registering Each Type (Code Example)

Hierarchical Taxonomy

register_taxonomy( 'topic', 'post', array(
  'label'        => 'Topics',
  'hierarchical' => true,
  'show_in_rest' => true,
) );

Non-Hierarchical Taxonomy

register_taxonomy( 'feature', 'post', array(
  'label'        => 'Features',
  'hierarchical' => false,
  'show_in_rest' => true,
) );

Can You Mix Both? (Yes — and You Should)

Most mature WordPress sites use both:

Hierarchical taxonomies for structure
Non-hierarchical taxonomies for attributes

This keeps your content organized without becoming rigid.

Common Mistakes to Avoid

Using tags as categories
Creating deep hierarchy when it’s not needed
Indexing hundreds of low-value tag archives
Letting editors freely create tags without guidelines

Quick Decision Guide

Is this a section of my site? → Hierarchical
Is this just a label or attribute? → Non-hierarchical
Will this appear in navigation? → Hierarchical
Is it used for filtering/search? → Non-hierarchical

Conclusion

Hierarchical and non-hierarchical taxonomies serve different purposes. Choosing the right one early prevents SEO issues, simplifies editing, and makes your WordPress site easier to scale.

Key takeaway:
Use hierarchical taxonomies for structure, and non-hierarchical taxonomies for flexible labeling.

🎨 Want to learn more? Visit our WordPress Customization Hub for tips and advanced techniques.