URL Processors

When to Use

Use this guide when you need to understand how facet selections are represented in URLs, or when customizing URL behavior.

Decision

Default URL format (query_string plugin):

https://example.com/search?search_api_fulltext=drupal&f[0]=category:tutorials&f[1]=tag:php&f[2]=price:[10 TO 50]

Part	Meaning
f	Filter key (configurable per facet source)
[0], [1], [2]	Array indices
category	Facet URL alias
:	Separator between alias and value
tutorials	The filter value
[10 TO 50]	Range syntax

URL configuration:

Setting	Where	Default	Purpose
Filter key	Facet source config	f	The URL parameter name
URL processor	Facet source config	query_string	The URL processor plugin
URL alias	Per-facet config	field name	The facet identifier in URLs

Pattern

Events for URL customization:

Event	When	Use Case
QUERY_STRING_CREATED	After building query string	Modify parameter format
ACTIVE_FILTERS_PARSED	After parsing URL params	Override active filter detection
URL_CREATED	After building facet link URL	Modify link destinations

Multiple facet sources on one page — Each facet source can have its own filter key. If two Views with facets appear on the same page, use different filter keys to prevent conflicts: - Source A: filter_key: 'f' - Source B: filter_key: 'g'

Common Mistakes

• Wrong: Changing the filter key on a live site → Right: Changing the filter key breaks all bookmarked faceted URLs. Plan before going live.
• Wrong: Two facets on the same source sharing the same URL alias → Right: URL alias conflicts break URL parameter handling.
• Wrong: Only blocking f[0] in robots.txt without the URL-encoded form → Right: f[0] becomes f%5B0%5D in URLs. Both patterns must be blocked. See SEO & Bot Protection.

See Also

• SEO & Bot Protection — URL implications for crawling
• Pretty Paths — cleaner facet URLs
• Reference: web/modules/contrib/facets/src/Plugin/facets/url_processor/