e. cannot be obtained by encoding any string of Unicode characters into UTF-8. Some sloppy decoder implementations may accept invalid byte sequences as input and produce a valid Unicode character as output for such a sequence. If one uses such a decoder, some Unicode characters have effectively more than one corresponding byte sequence: the valid one and some invalid ones. This could lead to security issues similar to the one described in the previous section. Therefore, if one wants to apply some filter (e. g. a regular expression written in UTF-8) to UTF-8 strings that will later be passed to a decoder that allows invalid byte sequences, one should canonicalize the strings before passing them to the filter. In this context, canonicalization is the process of translating every string character to its single valid byte sequence. An alternative to canonicalization is to reject any strings containing invalid byte sequences. URL A canonical URL is a URL for defining the single source of truth for duplicate content. Use by Google A canonical URL is the URL of the page that Google thinks is most representative from a set of duplicate pages on your site. For example, if you have URLs for the same page (for example https://example.com/?dress=1234 and https://example.com/dresses/1234), Google chooses one as canonical. Note that the pages do not need to be absolutely identical; minor changes in sorting or filtering of list pages do not make the page unique (for example, sorting by price or filtering by item color). The canonical can be in a different domain than a duplicate. Internet With the help of canonical URLs, a search engine knows which link should be provided in a query result. A canonical link element can get used to define a canonical URL. Intranet In intranets, manual searching for information is predominant. In this case, canonical URLs can be defined in a non-machine-readable form, too. For example in a guideline. Misc Canonical URLs are usually the URLs that get used for the share action. Since the Canonical URL gets used in the search result of search engines, they are in most cases a landing page. Search engines and SEO In web search and search engine optimization (SEO), URL canonicalization deals with web content that has more than one possible URL. Having multiple URLs for the same web content can cause problems for search engines - specifically in determining which URL should