Find every subdomain
of a domain.

Every hostname under a domain that ever appeared in a public TLS certificate — with certificate counts and first/last seen dates.

63 hosts · 245 ms

HostCertsFirst seenLast seen
busy.app 41 2026-04-18 2026-10-08
*.busy.app 37 2026-04-18 2026-10-08
grafana.busy.app 7 2026-05-25 2026-09-20
music.busy.app 6 2026-05-08 2026-09-03
helloworld.busy.app 8 2026-05-08 2026-09-04
prod.busy.app 2 2026-06-17 2026-06-17
*.prod.busy.app 2 2026-06-17 2026-06-17
cloud.prod.busy.app 4 2026-06-17 2026-06-17
mqtt.prod.busy.app 2 2026-06-17 2026-06-17
cloud.busy.app 12 2026-05-08 2026-09-04
mqtt.cloud.busy.app 2 2026-06-14 2026-06-14
www.cloud.busy.app 10 2026-05-08 2026-09-04
stage.busy.app 4 2026-04-15 2026-09-27
*.stage.busy.app 13 2026-04-15 2026-10-06
cloud.stage.busy.app 11 2026-06-09 2026-10-05
mqtt.cloud.stage.busy.app 4 2026-04-15 2026-09-27
api.stage.busy.app 10 2026-05-20 2026-09-15
apps-api.stage.busy.app 2 2026-09-03 2026-09-03
podinfo.stage.busy.app 4 2026-08-17 2026-09-09
mqtt.stage.busy.app 6 2026-04-15 2026-09-27
proxy.stage.busy.app 6 2026-04-15 2026-06-13
update.busy.app 10 2026-05-08 2026-09-03
posthog.busy.app 14 2026-06-10 2026-10-06
blog.busy.app 10 2026-04-27 2026-08-23
api.busy.app 11 2026-05-20 2026-09-15
apps-api.busy.app 2 2026-09-03 2026-09-03
img.email.busy.app 12 2026-05-23 2026-09-18
r.email.busy.app 4 2026-04-19 2026-09-26
cdn.busy.app 17 2025-08-20 2026-09-05
go.busy.app 15 2026-05-08 2026-09-03
www.go.busy.app 6 2026-05-08 2026-09-03
metrics.busy.app 11 2026-05-25 2026-09-20
docs.busy.app 10 2026-06-11 2026-10-07
logs.busy.app 7 2026-05-25 2026-09-20
alerts.busy.app 6 2026-06-29 2026-08-27
img.news.busy.app 6 2026-05-22 2026-09-17
r.news.busy.app 4 2026-04-20 2026-09-27
vault.busy.app 8 2026-05-08 2026-09-03
support.busy.app 9 2026-04-27 2026-09-06
*.test.busy.app 9 2026-06-10 2026-10-06
mqtt.busy.app 11 2026-05-10 2026-09-20
dev.busy.app 4 2026-05-07 2026-07-29
*.dev.busy.app 13 2026-05-07 2026-10-06
grafana.dev.busy.app 12 2026-05-08 2026-09-04
cloud.dev.busy.app 12 2026-06-09 2026-10-06
mqtt.cloud.dev.busy.app 4 2026-05-10 2026-08-01
blog.dev.busy.app 6 2026-07-10 2026-09-07
api.dev.busy.app 9 2026-05-20 2026-09-15
apps-api.dev.busy.app 2 2026-09-03 2026-09-03
internal.dev.busy.app 1 2026-09-29 2026-09-29
*.internal.dev.busy.app 1 2026-09-29 2026-09-29
alarm.dev.busy.app 2 2026-07-13 2026-07-13
metrics.dev.busy.app 10 2026-05-08 2026-09-03
logs.dev.busy.app 8 2026-05-08 2026-09-04
alerts.dev.busy.app 4 2026-06-29 2026-08-27
vault.dev.busy.app 10 2026-05-08 2026-09-04
mqtt.dev.busy.app 12 2026-05-10 2026-10-05
*.mqtt.dev.busy.app 2 2026-07-14 2026-07-14
recovery.dev.busy.app 8 2026-06-08 2026-10-04
proxy.dev.busy.app 2 2026-05-13 2026-05-13
www.busy.app 6 2026-04-27 2026-08-24
recovery.busy.app 8 2026-05-08 2026-09-03
sentry.busy.app 9 2026-06-04 2026-10-01

Programmatic access: API GET /v1/hosts/busy.app (API key for paging).

Shown here: hostnames with a certificate that is valid now or expired within the last 90 days. The full history since 2013 — hostnames whose last certificate expired earlier — is a Pro plan method: GET /v1/hosts-history/busy.app.