Glossary
TTL (Time To Live)
TTL is the number of seconds a DNS record may be cached before resolvers must fetch a fresh copy, controlling how fast changes propagate.
TTL (Time To Live) is a value, in seconds, attached to every DNS record that tells resolvers how long they may cache the answer before asking again.
How it affects you
- A high TTL (e.g.
86400= 24 hours) means fewer lookups and faster responses, but slower propagation of changes. - A low TTL (e.g.
300= 5 minutes) means changes spread quickly, at the cost of more query traffic.
Why it matters for hosting
TTL is the single most important setting when planning a migration. Before changing an a-record to point at a new host, lower the TTL a day or two in advance so the old value has expired everywhere. After the move stabilises, raise it again for efficiency.
Note that some resolvers ignore very low TTLs, and a separate zone-level minimum TTL governs how long negative (NXDOMAIN) answers are cached.
See also
DNS (Domain Name System)
DNS is the internet phone book that translates human-readable domain names like example.com into the IP addresses computers use to connect.
A Record
An A record is the DNS entry that maps a domain name to an IPv4 address, telling browsers exactly which server hosts the website.
Nameserver
A nameserver is a server that answers DNS queries for a domain, storing its zone records and telling the internet where the domain points.
Caching
Caching stores copies of data or pages so repeat requests are served instantly, reducing server work and dramatically speeding up websites.