Acceptable use & privacy

What this tool does

dnsutil.app is a free diagnostic tool for DNS, TLS, and NetScaler GSLB infrastructure. It traces DNS delegation paths, checks certificate chains, parses NetScaler GSLB configs, and — for the NetScaler checker's live verification feature — makes real outbound DNS lookups and TCP connections to confirm a pasted config matches what's actually deployed.

Acceptable use

Use this tool only against domains, servers, and infrastructure you own or are authorized to test.

This applies with particular force to the NetScaler config checker's “Verify against live DNS & reachability” feature: it opens real TCP connections to the IP addresses in whatever config you paste. Pasting someone else's configuration to probe their infrastructure without permission is not an acceptable use of this tool, regardless of what it technically allows.

Don't attempt to automate around the rate limits or daily usage limits, or use this service as a general-purpose network scanner. Known-private and reserved IP ranges (including cloud metadata addresses) are refused outright and never dialed, regardless of what a pasted config contains — this is an internal safety measure, not something to attempt to route around.

We may block or rate-limit traffic that we believe is abusive, at our discretion.

Privacy & data handling

No account or signup is required to use any feature.

An anonymous, randomly-generated cookie is used solely to apply fair-use daily limits per visitor — it isn't linked to your identity, and clearing it simply resets your own limits. We do not log requester IP addresses at the application level.

We do log aggregate, non-identifying activity for reliability and abuse-prevention purposes — which domain was looked up, how long a check took, and its outcome. We never store the full text of a NetScaler configuration you paste: it's parsed in memory to produce your result and then discarded. DNS and certificate results are cached briefly (about a minute) to avoid redundant lookups, not retained long-term.

The underlying hosting infrastructure (Google Cloud Run) keeps its own standard request-level operational logs independent of this application's own logging, as is normal for any web service.

Changes

This page may be updated as the tool changes. Material changes will be reflected here with an updated date above.