When building custom content filtering in WordPress — for blogs, product catalogs, or service directories — the tax_query parameter in WP_Query is one of the most essential tools. It allows developers to retrieve posts, pages, or custom post types based on specific taxonomy terms.

 What Are Taxonomies in WordPress?

Taxonomies in WordPress are ways of grouping content. WordPress comes with two default taxonomies:

  • category
  • post_tag

But developers can also create custom taxonomies, such as:

  • brand
  • region
  • product_type
  • skill_level

Each taxonomy contains terms — for example, a region taxonomy might include terms like europe, asia, or us.

 What Is a Tax Query?

A tax query is an array of conditions passed to WP_Query that tells WordPress to retrieve only content matching certain taxonomy terms.

Use cases include:

  • Showing blog posts from a specific category.
  • Displaying products filtered by attributes.
  • Creating dynamic filters for search or archives.

 Simple Example: Filter by Category

$args = array(
  'post_type' => 'post',
  'tax_query' => array(
    array(
      'taxonomy' => 'category',
      'field'    => 'slug',
      'terms'    => 'news',
    ),
  ),
);
$query = new WP_Query($args);

This will return all posts in the news category.

 Operators You Can Use

WordPress supports several operators in tax queries:

  • IN — match any of the terms (default)
  • NOT IN — exclude these terms
  • AND — must match all terms
  • EXISTS / NOT EXISTS — check if a taxonomy is set or not

 Advanced Example: Multiple Conditions

You can combine multiple taxonomy filters:

$args = array(
  'post_type' => 'product',
  'tax_query' => array(
    'relation' => 'AND',
    array(
      'taxonomy' => 'product_type',
      'field'    => 'slug',
      'terms'    => 'hosting',
    ),
    array(
      'taxonomy' => 'region',
      'field'    => 'slug',
      'terms'    => array('europe', 'us'),
      'operator' => 'IN',
    ),
  ),
);

This will return products that are of type hosting and available in either Europe or US regions.

Practical Uses

Some common use cases for tax queries in real-world WordPress projects:

  • A real estate site filtering listings by property type and location.
  • A job board showing jobs by department and seniority.
  • A WooCommerce store filtering products by brand, color, or availability.

 Summary

The tax_query parameter in WordPress empowers developers to build dynamic, relevant content displays. Whether you’re creating a filtered product grid, a search page, or a custom archive, tax queries allow you to fine-tune what content is shown to users — based on any taxonomy setup you’ve defined. Want to go further? Combine tax queries with meta queries or search parameters for even more powerful filtering.