“Propagation” is the time between changing a DNS record and everyone seeing the new value. Nothing is actually being pushed around the internet. Resolvers everywhere are holding cached copies of the old answer, and each one lets go when its copy expires.
Most record changes are visible everywhere within the record’s TTL, often 1 hour and at most a day or two. Changing nameservers can take up to 48 hours, because the .com (or other) servers’ NS records have long TTLs of their own.
Why it varies
- The old TTL decides the wait. If the record had a TTL of 86400 seconds (24 hours), a resolver that fetched it just before your change keeps the old answer for up to a day.
- Resolvers fetched at different times. That is why your colleague sees the new site while you still see the old one.
- Your own devices cache too. Your computer and browser keep answers for a short while. Flushing your DNS cache clears them.
Check what the world sees
Ask public resolvers directly, which skips your own caches:
dig example.com A @1.1.1.1 +short
dig example.com A @8.8.8.8 +short
dig example.com A +noall +answerThe last line shows the TTL counting down on your resolver’s cached copy, which tells you how long until it refreshes. Web-based “propagation checker” tools run the same query from many countries at once.
Make the next change fast
- A day or more before the change, lower the record’s TTL to 300 seconds (5 minutes).
- Wait at least as long as the old TTL, so every cached copy is the short-lived one.
- Make the change. Now the world catches up within about five minutes.
- Afterwards, raise the TTL back to something like 3600.
This is the core of changing hosts without downtime.
Something out of date? Software changes. If a step no longer works, tell us and we will check it and update the page.
