An SEO audit is a comprehensive review of a site for its visibility in search, covering three areas: technical (indexing, speed, structure, the mobile version), content (fit to phrases and intent, quality, cannibalisation) and links (the profile of links leading to the site). Its aim is to point out what is blocking higher positions and what to improve first, ordered by impact and effort. A good audit does not end with a list of errors, but with a concrete action plan and priorities. It is worth doing at the start of a collaboration and periodically, because the site, the content and search engine guidelines change. (Compare: SEO, SEO visibility, Keyword Cannibalization)