How long does DNS propagation take? TTL and migration checks

Why visitors see different servers

Resolvers can continue using an earlier answer until it expires. If a resolver cached an old address with a 3,600-second TTL five minutes before the change, it may continue using it for about 55 minutes. Reducing TTL to 300 at the time of the change does not shorten the lifetime of an answer already cached.

Plan the migration

1. Record existing records and TTLs for the root, www and any important subdomains. Back up mail records too.
2. Lower the TTL of records you will change at least one old TTL interval in advance.
3. Prepare HTTPS and important pages on the new host before switching DNS.
4. Keep the old host available during the overlap and plan how forms, accounts and orders will avoid writing to separate databases.
5. Restore the usual TTL after confirming the new site from several networks.

Check DNS and actual page content

Compare the authoritative answer, a public resolver and the browser result. If only the public resolver shows the old IP, a cache is likely. If both DNS answers are new but the page is old, inspect the CDN or host. Check www separately and verify AAAA as well as A.

Look beyond the web record’s TTL

Negative results can be cached for newly created names. Nameserver changes also involve the parent zone’s delegation and possibly a DNSSEC DS record. If all networks still fail after the expected wait, verify that you edited the authoritative zone and check its delegation rather than repeatedly changing records.