Concepts
Subdomains, records and TTL in two minutes.
Subdomain — a name you own under subdy.io, e.g. myapp.subdy.io.
Everything else hangs off it: records, certificates, usage stats.
DNS record — an instruction for resolvers. Subdy supports four types:
| Type | Points to | Example |
|---|---|---|
A | IPv4 address | 203.0.113.7 |
AAAA | IPv6 address | 2001:db8::7 |
CNAME | another hostname | myapp.fly.dev |
TXT | free text (verification, SPF…) | "v=spf1 -all" |
Record name is relative to your subdomain: @ is the subdomain
itself (myapp.subdy.io), www is www.myapp.subdy.io, * is a
wildcard that answers for anything not explicitly defined. A CNAME
must be the only record at its name — the API enforces this.
TTL (time to live, seconds) — how long resolvers may cache the answer. Low TTL (60–300) means IP changes propagate fast; higher TTL (3600+) means fewer queries. Default is 300.
Statuses: propagating (pushed to nameservers, seconds) →
active. Moderation can set suspended/frozen/banned — see
Security & abuse.
Certificates — every plan can order a wildcard certificate covering
myapp.subdy.io + *.myapp.subdy.io, issued via Let's Encrypt DNS-01
and renewed automatically ~30 days before expiry.