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DNS propagation checker

DNS propagation checker

Watch a DNS change spread across the internet, honestly. Four independent public resolver caches are queried straight from your browser and compared — with the TTL each cache returned counting down live to the moment it re-asks the source. A world-region view asks Google DNS with location hints for 12 cities to reveal GeoDNS and CDN steering, and watch mode re-checks everything on a timer during a migration, logging every answer change with a timestamp.

Where these queries go: every check runs straight from your browser to the public resolvers named on this page — Cloudflare, CF Security, Google, AliDNS, plus Google's DNS for the region view — over encrypted DNS-over-HTTPS. BRev has no server in the flow and never sees a lookup. Each resolver does see the queried name, under its own privacy policy.
What “DNS propagation” actually isTTL expiry, not a push

A DNS change is never pushed to the world's resolvers. Each resolver simply keeps the answer it last fetched until that answer's TTL (time to live) runs out, then asks the authoritative servers again. A DNS propagation checker like this one watches that process: it asks several independent caches the same question and shows you which have re-fetched your new record and which still hold the old one.

Why caches disagree for a while

Different resolvers filled their caches at different moments, so after a change they naturally disagree until every cache's TTL has expired. That window is bounded by the old record's TTL — a 24-hour TTL means up to 24 hours of mixed answers, no matter how fast your DNS host is. Anycast resolvers (Cloudflare, Google, AliDNS) are really many caches worldwide sharing one address, which is why even one “resolver” can flip back and forth briefly.

The migration playbook

A day or more before a planned change, lower the record's TTL (say to 300s) and wait for the old TTL to expire so the low value is what everyone caches. Make the change — the world now converges within minutes. Verify here, then raise the TTL back. During the switch, turn on watch mode above and leave the tab open: every answer flip is logged with a timestamp.

Negative caching — NXDOMAIN has a TTL too

If a name was queried before it existed, resolvers cache the “does not exist” answer (NXDOMAIN) for the time given by the zone's SOA minimum field. So a brand-new record can look “stuck” even though you just created it — that's negative caching expiring, not a failed change.

Need the full record detail — SOA serials, DNSSEC, CAA, reverse lookups? Use the DNS lookup tool for single-resolver inspection with zone-file and dig exports.