A canonical tag is an HTML tag that is inserted into the head section of a web page to indicate to search engines such as Google which content should be considered the original or main source when there are multiple similar or duplicate pages. This is especially important to avoid the problem of duplicate content, which can have a negative impact on search engine rankings.
How Canonical Tags Work
The Canonical tag, also referred to as rel=canonical, functions as a hint to search engines by indicating the original page or URL that should be preferentially indexed and displayed in search results. This can avoid search engine guesswork as to which version of a page is relevant, and thus avert potential ranking or indexing problems that can arise from duplicate content.
Application areas of Canonical Tags
- Related content: Two or more pages on a website contain similar content that cannot be considered completely independent. In this case, a canonical tag can be used to highlight the desired page.
- Duplicated content due to URL variations: If content on a page exists multiple times due to URL parameters or session IDs, this can lead to duplicate content. A canonical tag can help identify the original version.
- Pagination: In the case of multi-page articles or categories, several similar pages are created that nevertheless present individual content or products. In such cases, canonical tags are useful for communicating the correct structure to search engines and highlighting the original page to link to.
Canonical tags and SEO
Canonical tags are an important SEO element as they help avoid duplicate content and potential ranking problems. Search engines prefer unique, original content and can be penalized accordingly if they discover duplicate content. By using Canonical Tags, it is ensured that search engines can properly understand the original source of the content and position it accordingly in search results.