Web writing manuals (Canivet 2021, Gani 2018) give precise instructions to professional writers (De Angelis 2024). These practices can be analyzed based on the writings produced. For instance, SEO (Search Engine Optimization) is a practice which consists of optimizing the formulation of a digital writings (site, article, post, etc.) so that it obtains the best possible visibility in search engine results (Simonnot 2016). The optimization of writing allows texts to climb in PageRank, a prioritization process based on an algorithmic formula of the search engine to classify content on the Web. There are two levels of SEO: one called “natural” and the other “professional”. The first one (Canivet 2011; Andrieu 2014, 2015, 2021a, 2021b; Gani 2018) consists of three fundamental sub-practices: technical referencing concerning the stratification of the text according to the ergonomics of the site; semantic referencing which is done by a selection of keywords; hypertextual referencing which is done by the integration of hypertext links. But what does mean “referincing”? The algorithm guides the search engine in the search for relevance : these can be presented either in the form of keywords belonging to the same semantic field, also distributed in the metadata, or in the form of hyperlinks referring to texts that are part of the same discursive domain. The notion of “relevance” is a properly semiotic notion that Prieto (1975) transforms into a fundamental principle: the “principle of relevance”. What does the notions of “relevance” and “reference” mean in digital writing practices?