You change your A record, wait a few minutes, refresh the page — and your old site is still there. A colleague in another city says it already shows the new one. This is DNS propagation, and it trips up almost everyone the first time they migrate a website.
Why Propagation Takes Time at All
DNS resolvers — the servers that translate domain names to IP addresses on behalf of your device — cache records for a period defined by the TTL (Time to Live) value on each record. A TTL of 3600 means resolvers can cache the record for up to one hour before re-fetching it.
When you change a record, resolvers that already cached it will keep serving the old value until their TTL expires. There is no mechanism to broadcast "everyone please flush this domain" across the internet. Each resolver updates on its own schedule.
How Long Does It Actually Take?
The TTL on the record you changed is the main variable:
| TTL | Typical propagation |
|---|---|
| 300 (5 min) | 15–30 minutes for most of the world |
| 3600 (1 hour) | 2–4 hours |
| 86400 (24 hours) | Up to 48 hours in rare cases |
The practical trick: lower your TTL 24 hours before a planned migration. Drop it from 86400 to 300 the day before you change the actual record. Once propagation is complete, raise it again.
Why Different People See Different Results
Each person queries a different resolver — their ISP's resolver, Google 8.8.8.8, Cloudflare 1.1.1.1, or a corporate resolver. Each resolver has its own cache with its own expiry timer. They update independently, in no particular order.
Flushing your browser cache does not help here. The record is cached at the resolver level. You can flush your local OS DNS cache (ipconfig /flushdns on Windows, sudo dscacheutil -flushcache on macOS) to force your machine to re-query, but your ISP's upstream resolver might still have the old record.
How to Check Propagation
The DNS propagation checker runs a DNS lookup from dozens of global nodes simultaneously. You can see at a glance which regions are returning the new record and which are still on the old one.
Run it for your A record and AAAA record separately — TTLs can differ between record types. If you also changed your MX records for email, check those too. Email delivery can fail or route to the wrong server during the propagation window.
Nameserver Changes Take the Longest
Changing nameservers (NS records) is slower than changing regular records because it involves the TLD registry (.com, .de, .org, etc.) and its caches. The registry's TTL for NS delegation records is set by them, not by you — typically 24–48 hours.
During a nameserver change, queries can split between old and new nameservers. Make sure the old nameservers continue to serve the correct zone until propagation is complete.
Migrating Without Downtime
- Lower the TTL on affected records 24 hours before the change.
- Make the DNS change.
- Keep the old server running for the full original TTL duration after the change.
- Monitor propagation with the DNS check tool. Wait for all major regions to show the new values before decommissioning the old server.
- Raise TTLs again once fully migrated.