Paste your sitemap (the one with xhtml:link
alternates) and this checks the whole site at once — codes, duplicates, self-reference,
x-default, and whether every declaration is returned. One page's head works too.
Nothing is uploaded. The parsing and the checks happen in this tab.
Each row is one URL from your input, followed by the hreflang values it declares. A row that does not declare itself is a self-reference failure, which Google treats as an ignored set.