The same content can often be reached at several web addresses. With and without www, with and without a trailing slash, or through different parameters. To a human it makes no difference. To a search engine it does: it then sees several identical pages and does not know which is the real one. Canonicalisation solves this.
What is canonicalisation?
Canonicalisation is designating the official, preferred version of a page when several versions with the same or near-identical content exist. You do this with a canonical reference in the code, which says: this is the main version, treat it as the source.
Why is this important?
If search engines see several identical pages, they split the authority across all those versions. This weakens you. They may also choose the wrong version to show. Canonicalisation bundles the authority onto one version and prevents this fragmentation.
An example
An online shop shows the same product through several filter links, each with a slightly different address. Without canonicalisation, Google sees dozens of near-identical pages. With a correct canonical reference, Google knows it is one product and bundles all signals onto the main page.
What does this mean for you?
A clean, unambiguous structure in which every page has a clear address prevents confusion for search engines and AI. It is technical maintenance that is invisible to visitors but makes a big difference to how machines understand your site.
