Picking a TTL in practice
DNS TTL Explained: How to Look Up and Choose TTL Values
TTL stands for Time To Live. It is a number of seconds attached to every DNS record, and it answers one question: how long may a resolver reuse this answer before asking again?
It is the most under-considered setting in DNS. Most people accept whatever default their provider set and only discover it exists during an emergency migration, when it is too late to change it usefully.
Picking a TTL in practice
The trade-off
| High TTL (86400) | Low TTL (300) | |
|---|---|---|
| Lookup speed | Faster — usually cached | Slower — re-queried often |
| Query volume | Low | High |
| Change takes effect | Up to 24 hours | Up to 5 minutes |
| Resilience if your DNS fails | Better — caches cover you | Worse — caches expire fast |
| Best for | Stable records | Records about to change |
Key takeaway
High TTL optimises for speed and resilience. Low TTL optimises for agility. Neither is universally correct — the right answer depends on whether that record is about to change.
How to look up a DNS TTL: what it looks like in practice
example.com. 3600 IN A 93.184.216.34
example.com. 86400 IN NS ns1.example.com.To look up a domain's TTL, query the record with dig: it shows the remaining TTL, not the configured one. Run the same query twice a few seconds apart and watch the number drop — that is a live view of the resolver's cache counting down.
dig +noall +answer example.com
# wait 10 seconds, then
dig +noall +answer example.comRecommended values by record type
| Record | Suggested TTL | Why |
|---|---|---|
A / AAAA | 3600 (1 hour) | Good default: fast enough to fix mistakes, long enough to be efficient. |
A during a migration | 300 (5 min) | Set a day ahead so the change lands quickly. |
MX | 3600-14400 | Mail is queued and retried, so speed matters less. |
TXT (SPF/DKIM/DMARC) | 3600 | Changes rarely; fast enough when it does. |
NS | 86400+ | Delegation almost never changes and caching it reduces TLD load. |
CNAME | Match the target | No benefit to expiring faster than what it points at. |
The migration pattern
This is the one TTL workflow worth memorising, because it turns a day-long outage risk into a five-minute one.
At least one old-TTL period before the change, lower the TTL
If the current TTL is 3600, change it to 300 and wait at least an hour. Change nothing else.
Confirm the short TTL is being served
Query the record and check the TTL counts down from 300. Now every cache holding your record is on a five-minute timer.
Make the real change
Update the address. Maximum wait for anyone is now five minutes.
Verify, then restore the TTL
Once traffic is on the new server, set the TTL back to 3600 to stop paying the query cost.
TTL and resilience
There is a benefit to high TTLs that rarely gets mentioned: if your DNS provider suffers an outage, resolvers with your records still cached keep serving them. A 24-hour TTL can carry your domain through a multi-hour DNS outage largely unnoticed. A 60-second TTL means you go dark almost immediately.
This is a real argument for keeping TTLs comfortably high on stable records — and for treating low TTLs as a temporary migration tool rather than a default posture. What you are waiting for when a record changes is covered in DNS propagation.
Need to check a domain's public DNS addresses? Use the Domain IP Lookup tool.
Free tools for this topic
Frequently asked questions
Related reading
"Propagation" is really just caches expiring
0 min
you save the change
0-5 min
your DNS host updates
up to TTL
old answer still cached
after TTL
everyone sees the new one
Nothing is pushed anywhere -- each cache just stops reusing its copy
DNS Propagation Explained: Why Changes Take Time
Nothing propagates anywhere. Understanding what actually happens during the wait tells you exactly how long it will take and how to shorten it.
The records you will meet in nearly every zone
DNS A Records Explained: How Domains Map to IPv4
The record that actually points your domain at a server — its anatomy, the AAAA counterpart, and the four mistakes that break sites most often.
Picking a TTL in practice
How to Flush DNS Cache on Windows, macOS and Linux
Copy-paste commands for every platform — and the diagnostic that tells you whether flushing will help before you bother.