TTL (Time To Live) is a value in DNS records that specifies how long (in seconds) a resolver or browser may cache the record before it must query the authoritative DNS server again.

What is a good TTL for DNS records?

A TTL of 3600 (1 hour) is a common default. For frequently changing records, use 300-600 seconds. For stable records like NS and SOA, 86400 (24 hours) is fine.

Does a low TTL speed up DNS propagation?

Yes. A lower TTL means resolvers refresh the record more often, so changes propagate faster. The trade-off is more DNS queries, which increases load on your nameserver.

What is DNS TTL? Time To Live Explained

TTL (Time To Live) is a field in every DNS record that tells resolvers how long they can cache the record before fetching a fresh copy from the authoritative nameserver. TTL directly controls how fast DNS changes propagate across the internet.

A short TTL is fetched again and again and changes quickly; a long TTL is fetched once and changes slowly.

How TTL Works

When a resolver first looks up a DNS record, it caches the result for the number of seconds specified by the TTL. During this time, any query for the same record is served from cache — no DNS query to your nameserver occurs.

example.com.  3600  IN  A  203.0.113.1
              ^^^^
              TTL = 3600 seconds = 1 hour

After 3600 seconds, the resolver discards its cached copy and queries the authoritative nameserver again for a fresh record.

TTL Values and Their Impact

TTL	Duration	Use Case
`60`	1 minute	During active migration or failover testing
`300`	5 minutes	Records that change occasionally (good for planning migrations)
`3600`	1 hour	Common default — balance of freshness and performance
`86400`	24 hours	Stable records like NS and MX that rarely change
`604800`	7 days	SOA records and other very stable data

TTL Before a DNS Migration

The classic technique when planning a DNS change (e.g., moving to a new server):

48+ hours before: Lower your TTL to 300 seconds
Wait for the old high TTL to expire everywhere
Make the DNS change (e.g., update the A record IP)
Wait 5 minutes for the new TTL to propagate
After confirming everything works, raise TTL back to 3600+

This minimizes downtime because caches refresh quickly after the change.

SOA Minimum TTL

The SOA (Start of Authority) record contains a minimum TTL value that applies to negative responses (cache of "this record does not exist"). If you query for a record that doesn't exist, the resolver caches the "not found" result for this duration.

TTL Trade-offs

Low TTL	High TTL
Changes propagate quickly	Changes take longer to propagate
More DNS queries to your server	Fewer DNS queries (better performance)
Faster failover / recovery	Harder to change records quickly
Slightly higher DNS latency for users	Better caching — faster for users

Recommended TTL Values by Record Type

Record Type	Recommended TTL	Reason
A / AAAA	3600 (1h)	May change during server migrations
CNAME	3600 (1h)	Stable, but may change with CDN switches
MX	3600–86400	Mail servers rarely change
TXT (SPF/DMARC)	3600	Policy may need updates occasionally
NS	86400 (24h)	Very stable — only changes when switching DNS providers
SOA	86400	Rarely changes

Check Your Current TTL Values

Check DNS records and TTL →Next: How long does DNS propagation take? →

Try it on your domain

See the theory in practice — run a DNS Lookup for your own domain.