DNS Lookup

What does this tool do?

It asks the same DNS question to several public resolvers at once and shows you the answers grouped by what was said. When seven of them agree and one says something else, that is the thing worth looking at, and you should not have to compare rows by hand to find it.

Pick a record type and a domain. Everything happens in your browser, talking straight to each resolver over DNS-over-HTTPS, which is just HTTP.

What each answer tells you

The resolvers are asked in two ways. Three of them are asked plainly, with no hint about where the question comes from. Two of them — Cloudflare and Google — are asked again from four declared regions, using EDNS Client Subnet. That hint is what makes a resolver serving a geographically distributed domain hand back a different address for each region.

Sometimes the answers do not change between regions. That is information too, not a failure. A domain on an anycast network genuinely serves the same addresses everywhere, and a short list of one answer is the honest result. Where it does change, the map shows you at a glance which resolvers follow the region and which ones do not.

Along the way you also get the CNAME chain that leads to the final record, the TTL, and whether each resolver validated DNSSEC.

What this is not

This is not a propagation checker, and it is worth being precise about the difference. A propagation service queries from servers it owns in dozens of countries, so it can tell you what a resolver in São Paulo has in its cache right now.

We cannot see inside anybody’s cache. What you get here is what several resolvers answer when asked from a declared region, which answers the practical question — has my change taken effect, and does everybody see it the same way? — without pretending to a precision we do not have.

Two consequences worth knowing:

• Results are not perfectly reproducible. The same query a minute later can group differently. That is each resolver’s cache doing its job, not a bug.
• A resolver that does not answer is shown as such, in red, rather than quietly dropped.

Why it runs in your browser

A DNS lookup says something about you. If you are checking a domain before pointing it at a production site, or looking up an internal name, that is not something to hand to a third party just to render a table. There is no server on our side in this path: the queries go from your browser to the resolvers, and we never see them.

The world map is drawn from data built into the page, not from map tiles fetched from someone else’s server, for the same reason.