The canonical tag (rel="canonical") sits in the page head and points to the URL you want indexed. It is used when the same or very similar content is reachable at several URLs, such as with tracking parameters or sort orders.
It is a strong hint, not a command. Search engines may choose a different canonical if signals conflict.
Without canonicals, duplicate URLs split signals and waste crawl budget. Wrong canonicals, such as every page pointing to the homepage, can remove pages from the index.
VisibilityKit Crawler checks the canonical on every page, flags missing, conflicting and non-self-referencing canonicals, and shows which URLs point where.
It is good practice to include a self-referencing canonical on every indexable page.
Redirect when the duplicate URL should not be visited at all. Use a canonical when both URLs need to work for users.
The same or very similar content reachable at more than one URL.
Whether a page is able to be included in a search engine's index.
A directive telling search engines not to include a page in their index.
A 301 redirect signals a permanent move; a 302 signals a temporary one.
How many URLs a search engine is willing and able to crawl on your site in a given period.
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