DNS resolver comparison worksheet

Compare DNS answers you collected yourself from named resolvers. This page does not send DNS queries, and different answers or timestamps do not establish global propagation.

Paste two or more timestamped observations to compare resolver results.

Collect and enter observations

1. Run the same record name and type against each resolver, and note the resolver address or a clear label and the time with its timezone. For BIND dig, a command pattern is dig @<resolver-address> example.com A +noall +answer. With nslookup, specify the record type and server using that program's syntax.
2. Copy only the record data (RDATA) from each answer, not the owner name, TTL, class, or type. For multiple records, join each RDATA value with a semicolon. Use status answer for one or more returned records, nodata when the queried name exists but has no record of that type, nxdomain when the queried name does not exist, or timeout/error for the observed failure.
3. Enter four tab-separated columns per row: resolver label, ISO 8601 timestamp with Z or a UTC offset, status, answer data. For a status without records, enter - in the last column. Keep the query name and type the same across rows; record them in your notes because this worksheet compares only the text you enter.

Example command form: dig @<resolver-address> example.com A +noall +answer. BIND documents dig @server name type as a typical query form. Check your local nslookup help for its platform-specific syntax.

How the comparison works

• Rows are grouped by the resolver label you entered and ordered by timestamp. The summary compares each label's latest recorded status and answer set; it also lists all observations for context.
• Answer sets are compared as trimmed, case-sensitive text, with whitespace within each value collapsed and values sorted. TTLs are omitted from the comparison when you enter only RDATA, since TTLs can count down between observations.
• DNS records are cached according to TTL, and a local DNS cache can take longer to reflect a change. Observations may therefore differ because they were made at different times or through different caching paths. Repeat comparable queries and check the authoritative zone when appropriate.

This is a comparison aid for manually collected records, not a resolver test, authoritative-zone check, DNSSEC validator, or propagation monitor. It cannot confirm that two labels identify independent resolvers, that the same query parameters were used, or that every relevant resolver agrees. Do not treat the latest recorded answer as a global result.

Sources

• BIND 9 manual: dig DNS lookup utility — describes querying a specified server and the dig @server name type form; checked November 3, 2026.
• Cloudflare DNS: Time to Live (TTL) — describes record caching by TTL and notes that a local DNS cache may take longer to update; checked November 3, 2026.

For the distinction between a TTL planning window and measured resolver results, see the DNS TTL waiting window estimator. Use the DNS record format checker for local syntax checks of common record formats; it also does not query DNS.