"DNS propagation" is the time between changing a DNS setting and everyone on the internet seeing it. Nothing is actually pushed around the world: resolvers simply keep old answers in their cache until those answers expire. Understanding this makes migrations predictable.
Key terms
- TTL (time to live): the number of seconds a resolver may cache a record, for example
3600= one hour. - Resolver cache: the stored answers at your ISP, public DNS services, your router and your computer.
How long it takes
| Change | Typical time | Why |
|---|---|---|
| Edit a record (A, MX, TXT) | Up to the old record's TTL, often minutes to a few hours | Caches expire after the TTL. |
| Add a brand new record | Usually minutes | Nothing old is cached, unless a "not found" answer was cached. |
| Change nameservers | A few hours, up to 24 to 48 hours | TLD delegations carry long TTLs, often one or two days. |
Plan a change with little downtime
- A day before, lower the TTL of the records you will change to 300 seconds.
- Wait at least the old TTL so caches pick up the short value.
- Make the change. Most visitors move within minutes.
- Keep the old server running for a day or two for stragglers, then raise the TTL again.
Nameserver changes cannot be shortened this way, so keep both old and new hosting live during the switch. See migrating a website between hosts.
How to check progress
- Run
nslookup example.com 8.8.8.8andnslookup example.com 1.1.1.1to compare public resolvers. - Check nameservers with the WHOIS checker.
- Flush your own cache: on Windows run
ipconfig /flushdns; on macOS runsudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder.