How does faceted navigation impact SEO, & what are the best practices for implementing it to enhance user experience?

Faceted navigation can definitely impact SEO in both positive and negative ways, so it's important to implement it thoughtfully to get the user experience benefits while avoiding potential SEO pitfalls. Let me walk through some of the key considerations.

On the positive side, faceted navigation can enhance your site's architecture and make it easier for search engines to crawl and understand your product or content taxonomy. It allows crawlers to access additional content more efficiently and can even boost user engagement metrics that indirectly impact SEO like lower bounce rates.

However, some of the potential downsides are that faceted browsing generates a ton of URLs with query parameter filters that often lack semantic keyword relevance. This can create crawl budget issues if search engines waste resources crawling low-value filtered URLs with thin/duplicate content across them. It can also lead to diluting your link equity across many URLs rather than consolidating signals.

To optimize faceted navigation for both users and search engines, there are several best practice tactics I'd recommend:

First, limit the number of facets and nested filter levels you use to control how many parameter-based URLs get created. Use parent/child or breadcrumb link structures over parameters where you can.

Implement proper rel=canonical and robots meta tags to prevent duplicate content issues across your filtered URLs. You can also use robots.txt disallow to control what faceted URLs get crawled.

Leverage HTML5 pushState functionality to load faceted content dynamically without changing the URL string when possible.

Focus on adding rich keyword targeting to more important parent/subcategory pages rather than the individual facet parameter URLs themselves.

Monitor your crawl data in the Search Console to identify any wasted crawl budget on low-value filtered pages that could be blocked or canonicalized.

Utilize smart XML sitemaps including priority scoring to prioritize your most important URLs for crawlers.

And finally, be diligent about consolidating link equity onto your main category pages through your internal linking structure and hierarchy.

The overarching goal is creating a faceted browsing experience that delights users while using technical SEO tactics to guide search engines towards your most valuable URLs and product/content pages.