URL canonicalization issues arise when multiple URLs point to the same content but are not properly consolidated or canonicalized. This can happen due to URL parameters, URL case sensitivity, trailing slashes, or inconsistent URL formats. Search engines like Google may treat variations of the same URL as separate pages, leading to duplicate content problems and inefficient crawling and indexing. Webmasters should use canonical tags to specify the preferred URL version for indexing and ranking purposes, consolidate duplicate content variations, and use 301 redirects to redirect non-canonical URLs to the canonical version. To address URL canonicalization issues, webmasters should conduct URL audits, identify and consolidate duplicate content variations, and monitor index coverage and crawl errors in Google Search Console for indicators of canonicalization problems.