DNS Propagation Checker

Propagation depends on the TTL of the old record. TTL 86400 (24 hours) means caching resolvers keep the old value for up to 24 hours. TTL 300 (5 minutes) means fast propagation. To speed up a migration, lower the TTL to 300 a few days before the change — then change the record and propagation completes in minutes.

An A record maps a hostname to an IPv4 address. A CNAME maps a hostname to another hostname; the resolver follows the chain to find an A record. CNAME records cannot coexist with other records at the zone apex (root domain). Use ALIAS or ANAME records (where supported) for apex domain flexibility.

Each resolver has its own cache. After a DNS change, some resolvers still have the old record cached until its TTL expires. Others queried the authoritative nameserver recently and have the new record. This is what propagation means — all caches worldwide take time to expire and pick up the new value.

An MX record specifies which mail server handles email for a domain. The priority number (lower = preferred) allows fallback: if the primary server (priority 10) is unreachable, the sender tries the secondary (priority 20). Most domains today use a single MX pointing to Google Workspace or Microsoft 365.