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A wildcard may be used at the start of the name only, for example, "*.wikimedia.org". To search for external links to pages on Meta-Wiki, start with
meta.wikimedia.org/
The search pattern is case-sensitive after the first slash (/) after the host- or domain-name. If no protocol is specified, URLs with either the “http://” or “https://” protocol are returned. To search a single protocol or any other protocol, it must be given explicitly.
For performance reasons, a limitation to specific namespaces isn't possible.