Find every subdomain
of a domain.

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

100 hosts (first page) · 279 ms

HostCertsFirst seenLast seenDNS
duolingo.com 1 2025-11-25 2025-11-25 ok
*.duolingo.com 47 2025-07-22 2026-09-29 —
*.buildinghub-stage-2.duolingo.com 1 2026-05-19 2026-05-19 —
*.buildinghub-stage-3.duolingo.com 1 2026-05-19 2026-05-19 —
store-asia.duolingo.com 11 2026-06-02 2026-09-28 ok
grafana.duolingo.com 2 2026-09-08 2026-09-08 ok
okta.duolingo.com 9 2026-04-15 2026-09-17 ok
*.buildinghub.duolingo.com 2 2025-10-08 2026-09-08 —
vpc.duolingo.com 2 2025-11-09 2026-09-22 nodata
*.vpc.duolingo.com 2 2025-11-09 2026-09-22 —
infra-cicd-events-write-gateway-prod.duolingo.com 1 2026-08-27 2026-08-27 ok
grafana-cloud.duolingo.com 6 2026-07-21 2026-07-21 ok
*.buildinghub-stage.duolingo.com 2 2025-10-08 2026-09-08 —
*.infra-eks-stage.duolingo.com 2 2025-07-28 2026-06-28 —
*.stage-cluster-1.infra-eks-stage.duolingo.com 2 2025-10-21 2026-07-08 —
*.stage-cluster-2.infra-eks-stage.duolingo.com 2 2025-10-21 2026-07-08 —
*.stage-cluster-3.infra-eks-stage.duolingo.com 2 2025-08-12 2026-07-08 —
infra-cicd-events-write-gateway-stage.duolingo.com 2 2026-08-18 2026-08-18 ok
*.observability-stage.duolingo.com 2 2026-04-30 2026-09-30 —
*.obsv-stage-1.observability-stage.duolingo.com 2 2026-04-30 2026-09-30 —
*.sec-stage-1.security-stage.duolingo.com 1 2026-10-01 2026-10-01 —
circle.duolingo.com 3 2026-04-17 2026-06-17 ok
*.pe.duolingo.com 4 2026-04-30 2026-09-30 —
*.obsv-prod.pe.duolingo.com 1 2026-05-18 2026-05-18 —
*.obsv-stage.pe.duolingo.com 1 2026-05-18 2026-05-18 —
develocity.pe.duolingo.com 4 2026-04-10 2026-09-02 ok
drv.develocity.pe.duolingo.com 4 2026-04-10 2026-08-17 ok
store.duolingo.com 13 2026-05-23 2026-10-02 ok
grafana-us-central-azure.duolingo.com 2 2026-09-08 2026-09-08 ok
grafana-cloud-us-central-azure.duolingo.com 4 2026-07-21 2026-07-21 ok
blog.duolingo.com 7 2026-06-18 2026-09-26 ok
research.duolingo.com 5 2026-04-29 2026-08-27 ok
grafana-us-east-oh.duolingo.com 2 2026-09-08 2026-09-08 ok
grafana-cloud-us-east-oh.duolingo.com 4 2026-07-21 2026-07-21 ok
push.duolingo.com 1 2025-11-07 2025-11-07 ok
www.push.duolingo.com 1 2025-11-07 2025-11-07 ok
jenkins-ci.duolingo.com 1 2025-12-04 2025-12-04 ok
delphi.duolingo.com 1 2026-04-17 2026-04-17 ok
*.platform-api-prod-1.platform-api.duolingo.com 1 2026-06-23 2026-06-23 —
*.plat-api.platform-api.duolingo.com 1 2026-06-25 2026-06-25 —
sharedtask.duolingo.com 5 2026-04-30 2026-08-28 ok
*.internal.duolingo.com 7 2025-06-24 2026-09-03 —
*.buildinghub-stage-2.internal.duolingo.com 1 2026-05-19 2026-05-19 —
*.buildinghub-stage-3.internal.duolingo.com 1 2026-05-19 2026-05-19 —
*.buildinghub.internal.duolingo.com 2 2025-07-17 2026-06-17 —
*.buildinghub-stage.internal.duolingo.com 2 2025-07-17 2026-06-17 —
*.client-platform.duolingo.com 2 2026-08-11 2026-08-11 —
unity-license-server.client-platform.duolingo.com 1 2026-06-25 2026-06-25 ok
gpn.duolingo.com 6 2026-04-27 2026-08-23 ok
qr-gpn.duolingo.com 1 2026-09-07 2026-09-07 ok
go.duolingo.com 9 2026-04-19 2026-09-16 ok
grafana-us-east-gcp.duolingo.com 2 2026-09-08 2026-09-08 ok
grafana-cloud-us-east-gcp.duolingo.com 4 2026-07-21 2026-07-21 ok
englishtest-desktop.duolingo.com 1 2026-01-05 2026-01-05 ok
*.obsv-prod-1.k8s.duolingo.com 1 2026-02-18 2026-02-18 —
*.obsv-stage-1.k8s.duolingo.com 1 2026-02-18 2026-02-18 —
*.prod-cluster-1.k8s.duolingo.com 2 2025-10-29 2026-09-29 —
*.stage-cluster-1.k8s.duolingo.com 2 2025-10-29 2026-09-29 —
*.dev-cluster-1.k8s.duolingo.com 3 2026-04-19 2026-09-19 —
*.obsv-dev-1.k8s.duolingo.com 1 2026-02-18 2026-02-18 —
*.prod-cluster-2.k8s.duolingo.com 3 2025-10-16 2026-09-16 —
*.stage-cluster-2.k8s.duolingo.com 3 2025-10-16 2026-09-16 —
*.dev-cluster-2.k8s.duolingo.com 2 2025-10-03 2026-09-03 —
*.prod-cluster-3.k8s.duolingo.com 3 2026-03-19 2026-08-19 —
*.prod-cluster-4.k8s.duolingo.com 1 2026-09-28 2026-09-28 —
wingctl-api.k8s.duolingo.com 1 2026-01-23 2026-01-23 ok
*.det-stage-1.det-stage-eks.duolingo.com 1 2026-10-02 2026-10-02 —
*.det-dev-1.det-stage-eks.duolingo.com 1 2026-10-02 2026-10-02 —
*.det-prod-1.det-eks.duolingo.com 1 2026-10-02 2026-10-02 —
employee-tools.duolingo.com 1 2025-12-28 2025-12-28 ok
email.careers.duolingo.com 4 2026-04-23 2026-06-22 ok
investors.duolingo.com 16 2026-04-24 2026-10-01 ok
artifacts.duolingo.com 1 2025-09-04 2025-09-04 ok
prod.artifacts.duolingo.com 3 2025-09-10 2026-08-11 ok
*.ca-prod-1.cloud-agents.duolingo.com 1 2026-05-29 2026-05-29 —
email.events.duolingo.com 3 2026-04-15 2026-06-14 ok
status.duolingo.com 5 2026-04-29 2026-08-26 ok
podcast.duolingo.com 5 2026-05-01 2026-08-29 ok
grafana-cloud-obsv-test.duolingo.com 8 2026-07-28 2026-09-26 ok
blog.englishtest.duolingo.com 7 2026-06-20 2026-09-28 ok
trust.englishtest.duolingo.com 13 2026-05-21 2026-09-17 ok
www.englishtest.duolingo.com 1 2026-01-05 2026-01-05 ok
*.fallout-prod-1.fallout.duolingo.com 1 2026-06-23 2026-06-23 —
store-eu.duolingo.com 14 2026-04-14 2026-09-27 ok
*.platform-api-dev.duolingo.com 1 2026-05-07 2026-05-07 —
*.platform-api-dev-1.platform-api-dev.duolingo.com 3 2026-05-07 2026-05-08 —
*.platform-work-prod.platform-api-dev.duolingo.com 1 2026-09-20 2026-09-20 —
*.platform-work-stage.platform-api-dev.duolingo.com 1 2026-09-20 2026-09-20 —
wingctl-api.platform-api-dev.duolingo.com 1 2026-05-26 2026-05-26 ok
*.platform-work-dev.platform-api-dev.duolingo.com 1 2026-05-15 2026-05-15 —
infra-ack-dev.duolingo.com 2 2026-09-07 2026-09-07 nodata
*.infra-ack-dev.duolingo.com 2 2026-09-07 2026-09-07 —
*.test.infra-ack-dev.duolingo.com 1 2026-09-22 2026-09-22 —
*.yangyang-dev.infra-ack-dev.duolingo.com 1 2026-09-22 2026-09-22 —
*.leo-dev-2-1.infra-eks-dev.duolingo.com 1 2025-11-12 2025-11-12 —
*.dev-cluster-1.infra-eks-dev.duolingo.com 1 2026-09-04 2026-09-04 —
*.noyama-dev-1.infra-eks-dev.duolingo.com 1 2025-09-02 2025-09-02 —
*.emma-dev-1.infra-eks-dev.duolingo.com 1 2025-07-01 2025-07-01 —
*.tmac-dev-1.infra-eks-dev.duolingo.com 1 2025-08-26 2025-08-26 —
*.guadalupe-dev-1.infra-eks-dev.duolingo.com 2 2026-08-21 2026-08-21 —

Showing the first 100 hostnames — sign in with GitHub or Google to page the full list, or use the API with an API key: GET /v1/hosts/duolingo.com.

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/duolingo.com.