DNS History lists A, AAAA, CNAME, MX and NS values IPTOOL has observed, with first and last seen dates. Lookups, domain reports, member DNS watches and periodic crawls feed the archive.
Entering a domain also runs a live resolve and updates the store. Entering an IP lists hosts we saw pointing at that address (neighbor / reverse-IP inventory).
This is not a dnshistory.org-scale global archive. Coverage grows with observations on this site; an empty result often means “not seen yet”, not “never existed”.
Unique (host, type, value) rows keep first_seen / last_seen. Seeing the same value again bumps last_seen and the counter; old values remain after a change.
A background crawl re-checks names from query_log and watches about weekly, so A/CNAME changes accumulate in the archive over time.