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This page reports DNS seeder reachability for the seeders used by the crawler configuration. Bitcoin nodes join the peer-to-peer network by initially making outgoing connections to peers announced by these seeders via A (IPv4) and AAAA (IPv6) DNS records, so high availability is important for reliable bootstrapping.
The default list of DNS seeders follows the reference implementation seeders used by Bitcoin Core. Standalone deployments show live DNS resolution; seven-day historical network, user-agent, and service-prefix samples are only shown when a deployment provides that data source.