I am working for a project that has multi facet filters. The url that will be build when faceting applied will have several delimiters. I am not sure what characters should I use as delimiter that are SEO freindly and does not impact SEO negatively.
The rule of thumb for "SEO friendly URLs" is to create URLs that convey their content in a meaningful and easy to understand way to a human user. An approach I like is
facetName=facetValue (so no facetIDs or facetCodes that the user can not interpret).
Since your question is specifically about delimiters for multifaceted pages, you are referring to the "query part" of a URL. That means you should use the
& character to separate the facets so it would look something like this
A query string. If a query string is used, it follows the path component, and provides a string of information that the resource can use for some purpose (for example, as parameters for a search or as data to be processed).
The query string is usually a string of name and value pairs; for example, term=bluebird.
Name and value pairs are separated from each other by an ampersand (&); for example, term=bluebird&source=browser-search.
Lastly, in case your facet value is more than on word use
- between them.
You can read a great deal of things about URL formatting here --> RFC 1738