Global DNS propagation checker

Nothing actually propagates

DNS changes are not pushed anywhere. Your authoritative servers publish the new value immediately; the rest of the internet keeps serving the old one until the copy it cached expires. That is what the TTL of the record controls.

So a resolver still answering with the old value is not broken: it is simply inside the TTL window. If you plan a migration, lower the TTL a day in advance, make the change, then raise it again.

Why some resolvers never agree

Large providers answer from the closest datacentre, so two people can get different addresses on purpose. Anycast, GeoDNS and load balancing all produce legitimate differences that look like a propagation problem.