DNS TTL and Propagation Explained
dns ttl explained · dns propagation time · how long dns changes take
What DNS TTL means, realistic propagation timelines, lowering TTL before migrations, and verifying updates with DNS Checker vs propagation maps.
By DN01 Network Team
TTL (Time To Live) tells resolvers how long they may cache an answer. DNS propagation is not instant teleportation — it is old caches expiring and new queries picking up updated authoritative data.
DN01 DNS Checker shows current answers from our resolver path — ideal for confirming your change published. Regional propagation maps compare many resolvers worldwide over time; use both mindsets during cutovers.
Planning a low-TTL window
Drop TTL to 300 seconds 24–48 hours before a change on stable records. Make the change at authoritative DNS. Verify with DNS Checker. Raise TTL again after stability returns.
Some registrars ignore low TTL minimums — read their docs. SOA refresh/retry timers matter for zone transfers but not public resolver caches the same way TTL does.
Why different tools show different answers
Recursive resolvers cache independently. Your laptop, office DNS, and 8.8.8.8 may disagree until TTLs expire. Authoritative NS should agree immediately — query them with DIG @ns1.example.com if in doubt.
Changing nameservers adds registrar glue propagation on top of record TTL — allow up to 48 hours for full global convergence even with low TTL.
Frequently asked questions
- Is propagation the same as TTL?
Related but not identical. TTL drives cache expiry; propagation describes the global convergence as caches refresh.
- Can I flush Google DNS cache?
Public resolvers do not offer per-user flush. Wait for TTL or query authoritative NS directly.
- What TTL do CDNs use?
Often low for orange-cloud proxied names; origin may differ. Check both in DNS Checker when debugging.