Field notes · August 2026
Notes on how SubdomainData works, what a public hostname can establish, and the internet datasets that become useful once their clocks, coverage, and inference limits stay visible.
SubdomainData snapshots a public hostname index once a day, records changes observed after launch, and leaves the first import's dates unknown. The result is a reproducible history, not a census of active Slack customers.
A public slack.com hostname is a useful observation with narrow meaning. It is not proof of workspace creation, present activity, company ownership, headcount, plan, or security posture.
Certificate logs, web crawls, registration records, zone files, routing collectors, archives, and active measurements can answer narrow questions about the public internet. Their limits matter as much as their scale.