Every lookup is made from resolvers we operate, in our own data centres in Dhaka and Miami. Nothing here is a wrapper around somebody else's API, which is why a result can say where it was resolved from and why there is no rate limit for ordinary use.
Queries are made over EDNS0 with a TCP fallback, so a large record set is read completely rather than truncated. That detail matters more than it sounds: a truncated reply is how a checker ends up reporting that a domain has no SPF record when it plainly does.
Reports are not listed, indexed or shared, and they are not advertised anywhere. Anyone holding the link can read the report, so treat the link the way you would treat the result.
Site previews expire on their own after seven days. A preview only affects a device whose owner has deliberately pointed it at our resolver, and no site traffic passes through us at any point.
Write to [email protected]. If you are reporting a wrong answer, include the domain and the report link: a check that returns something incorrect is treated as a serious bug, not a cosmetic one.