What Is TTL

Introduction

TTL is measured in seconds. A TTL of 300 means resolvers may cache the record for five minutes. A TTL of 3600 means one hour.

TTL matters most before migrations and DNS changes when you want old cached values to expire sooner.

Quick answer

What it means

Every DNS record can have a TTL. While cached, resolvers return the stored answer without querying your authoritative nameserver on every lookup.

• Controls DNS caching duration
• Lower TTL before planned migrations
• Raise TTL after DNS is stable to reduce load
• Old cached values persist until previous TTL expires
• SOA minimum TTL is a zone default, not every record's TTL

Where you see this:

• Planning website or email DNS migrations
• Reducing downtime risk during IP changes
• Understanding why some users still see old DNS
• Balancing propagation speed vs DNS query volume

300 seconds  = 5 minutes
3600 seconds = 1 hour
86400 seconds = 24 hours

Why this matters

How to check it

1. Run DNS Lookup and note TTL on key records (A, MX, TXT).
2. Check TTL before migration and lower it 24–48 hours ahead if possible.
3. Use dig example.com A to see TTL in command output.
4. After migration stabilizes, consider raising TTL again.
5. Remember local device and browser DNS cache may add extra delay.

Common mistakes

Example

example.com.  300   IN  A  192.0.2.10   ; 5 min cache
example.com.  3600  IN  A  192.0.2.10   ; 1 hour cache

Frequently asked questions