Time to live (TTL)

In DNS, time to live (TTL) is the number of seconds a record may be cached before it should be refreshed.

Format
Domains & DNS
Updated
Updated
Glossary Domains & DNS
Time to live Also known as TTL.Aliases: DNS TTL, cache lifetime.

Definition

In DNS, time to live (TTL) is the number of seconds a record may be cached before it should be refreshed.

How it works

Every DNS answer carries its TTL, and resolvers reuse the answer for that many seconds before asking again. It is a trade-off dial: long TTLs mean fewer queries but slower changes; short ones mean the opposite. Before a migration, lower the TTL well in advance — answers already cached under the old, longer TTL will live out their full term regardless.

Example: A TTL of 3600 lets a resolver cache the answer for up to one hour.

Often confused: Lowering a TTL speeds up future changes only; it cannot recall answers already sitting in caches under the old value.

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Sources

Last reviewed 2026-07-19.