You changed an A record, refreshed the site, and… it’s
still pointing at the old server. Nothing is broken — you’re watching DNS
propagation, and it’s almost always about one number: TTL.
There’s no single “DNS” to update
It helps to stop thinking of DNS as one database. When you change a record at your provider, the authoritative answer updates instantly — but the rest of the internet is full of resolvers (at ISPs, public services like 8.8.8.8, and on devices) that cached the old answer and will keep serving it until that cache expires.
- You update the record at your DNS provider
- Authoritative servers serve the new value immediately
- Cached resolvers keep the old value until TTL expires
- Caches refresh — everyone now sees the new value
TTL is the timer
Every record has a TTL (time to live) in seconds — how long resolvers are
allowed to cache it. A TTL of 3600 means a resolver can serve a stale answer
for up to an hour after your change. Propagation isn’t a mysterious delay; it’s
just the longest TTL among everyone who cached the old record.
How to check it
Because different resolvers update at different times, the way to check propagation is to ask several of them and compare. If they agree, you’re done; if they don’t, some caches are still holding the old value.
Check whether a change has spread with the DNS propagation checker, or see a domain’s full records with the DNS lookup tool.