Turn your WordPress post categories into a search powerhouse! This plugin gives you a set of dropdown menus based on parent categories and their sub-categories. Users select one sub-category per parent, and the plugin filters posts matching the selected combination.

Available as:

Gutenberg Block — “Multi-Category Filter” in the block inserter (new in v4)
Classic Widget — “Multi-Category Selection” in Appearance > Widgets
Shortcode — [mcsw] on any page or post

Features:

AND / OR category filtering — find posts matching ALL or ANY selected categories
AJAX chained drilldown — selecting a parent dynamically loads its children
Pretty permalink URLs (/categories/3,5/search_type/and/order/title/)
Ordering by title or default
Configurable blank search behavior
Exclude specific categories
Lightweight — no jQuery, no external dependencies
Pagination support
Display form above results on category pages (optional)

Sample use case:

Real estate — set up parent categories like “Bedrooms”, “Bathrooms”, “Price Range” with sub-categories beneath them. Users filter listings by selecting from each dropdown.

Upgrading from v3.x:

PHP sessions have been removed entirely — the URL now carries all state, which means better compatibility with caching plugins, load balancers, and modern hosting
jQuery has been replaced with vanilla JavaScript
CSS classes have changed from wpmcsw/wpmm to BEM-style mcsw-* classes — update any custom CSS
The old select-chain.js in the plugin root has been replaced by js/select-chain.js

Multiple Category Selection Widget