Kanonische URL – Definition

A canonical URL is the preferred link to a web page, telling search engines which version of a page that exists in multiple variants should be treated as the primary one.

Duplicate content is common in e-commerce environments: product pages with different filter parameters, category pages with sorting options, or multilingual variants of the same page. Canonical tags stop search engines from evaluating these duplicates separately and splitting SEO weight across many variants. In a CMS context, canonical tags should be set automatically — per market, per language — without manual work on every single page. A subtle but common mistake is setting the canonical tag to the wrong URL variant — pointing to a version with tracking parameters, or to a URL that itself redirects, which confuses crawlers rather than clarifying intent. Canonical logic also needs to account for pagination carefully: a paginated category listing generally shouldn't canonicalize to page 1, since that signals to search engines that additional pages don't matter, potentially hiding legitimate catalog content from being indexed.