x-default: a routing fallback that is not a language
The x-default entry tells a search engine where to send a reader whose language is not covered. It names no language, so it is not counted here. Counting it would add one to every well-configured site and nothing to a badly configured one. As of 2026-09-22.
| Consideration | Effect of counting it | Effect of excluding it |
|---|---|---|
| Comparability | Rewards good configuration, not coverage | Counts only named languages |
| Well-configured sites | Every count rises by one | Unaffected |
| Sites without it | Appear one language behind | Unaffected |
| Information lost | None | The existence of a fallback page |
Inclusion rule. The two possible treatments of one entry, with the consequence of each. The register applies the second to every vendor. Order. Fixed order, comparability first.
1A hint about routing, not about language
The entry exists so that a reader whose language nobody has covered lands somewhere sensible rather than on a guess. It is a statement about fallback behaviour, and it carries no language name at all.
That is the whole argument for leaving it out. A column counting languages that included an entry naming none would be counting something else, and the something else is how carefully a site was configured.
2The cost of excluding it is small and real
What is lost is the knowledge that a fallback page exists, which is genuinely useful to somebody auditing a site. It is not useful for comparing language coverage, which is what this column does.
A reader who wants that information can read the markup, which is where every figure in this column comes from. The rule is written down so the difference between the two readings is visible rather than buried.
3Small decisions are what make a count reproducible
This entry, and alternates pointing at other hosts, are the two places where two careful people counting the same page would disagree. Fixing both in writing is what turns a number into something a reader can re-derive.
A count nobody else can reproduce has no business being published, however carefully it was made. Recording the exclusions is cheaper than defending the totals later.
A definition, not a measurement: no vendor figure appears here that is not also in the register. The other exclusion, alternates on other hosts, is covered by the same-host rule.
Nearby terms: hreflang attribute, lang attribute. The whole vocabulary is at terms; nothing on this page is a claim about a named product.