What this checks
This tool asks several independent public DNS resolvers — Cloudflare, Google, Quad9, OpenDNS, and Level3 — for a domain's A records at the same moment, then compares their answers. If every resolver that responded returns the same set of addresses, your change has settled everywhere those resolvers can see. If they disagree, some are still serving an older cached answer, and propagation is still in progress. The verdict at the top summarizes the result; the table shows exactly what each resolver returned and how long it took.
Propagation is TTL expiry, not a push
"Propagation" makes it sound like your change is being pushed out across the internet, but nothing is being pushed. When you edit a record, your authoritative nameservers update immediately. Everyone else is a resolver that cached the old answer, and it keeps serving that cached copy until the record's TTL expires and it re-queries. So propagation time is really just the longest remaining TTL out there — there's no global broadcast, only a scattering of caches quietly timing out and refreshing on their own schedules.
Negative caching
There's a subtler trap: resolvers cache absence too. If you check a name before you've created its record — or a monitoring tool did — the resolver caches the "no such record" answer for a period governed by your zone's SOA minimum (negative-cache TTL). After you add the record, that resolver can keep insisting the name doesn't exist until the negative cache expires, even though the record now exists. It's a common reason a brand-new record seems to "not propagate" to one resolver while working elsewhere.
Why some resolvers lag
Each resolver is really a fleet of caching servers in many locations, and they didn't all fetch your record at the same instant, so they don't all expire at the same instant. A big public resolver you hit from one region may be a different physical cache than the one another user hits, each with its own countdown. That's why a single resolver can still show the old value minutes after the others have updated — it simply cached the previous answer slightly later, and its TTL hasn't run out yet.
FAQ
How long does DNS propagation take?
Up to the record's TTL for most resolvers, so a value from a few minutes to a few hours depending on what the TTL was set to before your change. The old TTL is what governs how long stale copies linger, not the new one. Most changes are visible nearly everywhere within an hour when TTLs are reasonable.
Can I speed it up?
Only in advance. Lower the record's TTL a day or two before a planned change, so caches everywhere expire quickly around the cutover; then raise it again afterward. Once a change is already live you can't force the world's resolvers to drop their caches early — you can only wait out the TTL they fetched under.
Why does one resolver still show the old value?
Because that resolver cached the previous answer and its TTL hasn't expired yet, or it's a different cache node than the ones that already updated. Give it until the old TTL elapses. If a brand-new record is the one missing, suspect negative caching — the resolver may have cached "no such record" before you created it.
Does flushing my local cache help?
Only for you. Flushing your operating system or browser DNS cache clears your own machine's copy, so you'll see the current answer sooner locally — but it does nothing for the public resolvers your visitors use. This tool queries those public resolvers directly, so it already bypasses your local cache.