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OpsKit

DNS Tools - Lookup, Propagation Checker, Reverse DNS, MX, SPF, DMARC & Zone Checks

Free browser-based DNS tools for developers, DevOps teams, sysadmins, and hosting providers. Run DNS lookups, compare propagation, check reverse DNS, inspect nameservers, validate mail DNS, and generate records.

DNS Lookup

Lookup inputs

Quick examples

What this answers quickly

  • What record values are visible right now?
  • Is the hostname returning the record type I expect?
  • Do public resolvers agree or already diverge?
  • What terminal commands should I run next?
One resolver failed, but partial lookup data is still available.
Propagation Checker

Comparison inputs

Quick examples

Use this when

  • one network sees old data and another sees new data
  • you want a cleaner resolver diff than a map-style propagation site
  • you need to compare answers against the value you expected
One resolver failed, but comparison data is still available.
Reverse DNS Lookup

Reverse lookup

Quick examples

Typical use cases

  • mail server reverse DNS checks
  • quick server identity validation
  • support triage for IPs that should map to a hostname
Nameserver / Zone Check

Zone inputs

Quick examples

Useful for

  • finding the likely zone apex behind a hostname
  • reviewing NS and SOA context during provider setup
  • spotting obvious delegation mismatches
Mail DNS Check

Mail DNS inputs

Quick examples

Checks included

  • MX targets and priorities
  • SPF record presence and duplication hints
  • DMARC policy lookup under _dmarc
  • optional DKIM selector lookup
DNS Record Generator

Record inputs

Quick examples

Copy a starter record, then adapt it in your DNS provider UI or zone file.

IP Blacklist (DNSBL) Checker
Blacklist check





Quick examples


Why this matters
  • Mail servers silently reject or quarantine mail from blacklisted IPs
  • A single DNSBL listing can cause delivery failures across many recipients
  • Regular checks help catch listings before they impact operations
Advanced troubleshooting
Need deeper resolver and cutover workflows?
Use DNS Ops Lab for resolver drift investigation,
NXDOMAIN cache analysis, cutover planning, and alias tracing.
Open DNS Ops Lab
What This DNS Tools Page Helps You Do
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This page is designed for the DNS checks people run all the time:
  • look up live records for a hostname
  • compare answers across public resolvers
  • verify reverse DNS for an IP address
  • inspect nameserver and SOA context
  • validate MX, SPF, DMARC, and DKIM lookups
  • generate copyable DNS records for common setups
  • check if an IP is on DNS-based blacklists (DNSBLs)
The goal is speed and clarity. You should be able to answer the usual DNS questions without dropping into a more complex incident-focused workflow.
Included Modules
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DNS Lookup
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Check common record types such as A, AAAA, CNAME, MX, TXT, NS, SOA, CAA, and PTR. The page summarizes what was found and keeps copyable dig commands close to the results.
Propagation Checker
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Compare multiple public resolvers side by side so you can see whether an apparent propagation problem is actually resolver cache divergence.
Reverse DNS Lookup
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Run PTR lookups for IPv4 or IPv6 addresses and quickly review whether the returned hostname makes sense for mail or server identity workflows.
Nameserver / Zone Check
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Inspect likely zone apex, authoritative nameservers, and SOA context when you are debugging delegation or provider setup issues.
Mail DNS Check
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Review MX, SPF, DMARC, and optional DKIM selector lookups from one place. This is useful for everyday domain onboarding and mail routing validation.
DNS Record Generator
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Generate clean example records for A, AAAA, CNAME, MX, TXT, SPF, DMARC, SRV, and DKIM starter snippets.
IP Blacklist (DNSBL) Checker
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Check whether an IPv4 address is listed on open DNS-based blacklists. The tool queries 7 public DNSBLs in parallel and shows which lists return a positive result.
Privacy Model
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OpsKit does not proxy these DNS requests through an application backend.
  • DNS lookups are performed from your browser against public DNS-over-HTTPS endpoints
  • no account or cookie is required to use this page
  • no localStorage is used for the tool state in this version
Public resolvers still see the query, so treat this as a convenient operational tool, not an anonymity service.
Common DNS Problems and What To Check First
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The site still resolves to the old IP
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Start with the propagation checker. If public resolvers disagree, you are usually looking at cache divergence rather than a mysterious global propagation map problem.
A new hostname returns NXDOMAIN
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Check the zone view and the DNS lookup result together. If the zone exists but the RRset does not, you may be seeing a record-level issue instead of a delegation problem.
Email setup is failing
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Run the mail DNS check and confirm:
  • MX targets exist
  • there is only one effective SPF policy
  • DMARC is published under _dmarc
  • the DKIM selector hostname is correct
Reverse DNS looks suspicious
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Use the reverse DNS module, then confirm whether the returned hostname maps back to the same service or IP family you expected.
Command-Line Reference
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# Basic record lookup
dig example.com A
dig example.com MX
dig example.com TXT

# Compare recursive resolvers
dig @1.1.1.1 example.com A
dig @8.8.8.8 example.com A

# Reverse DNS
dig -x 203.0.113.10

# Zone and delegation context
dig example.com NS
dig example.com SOA

# Mail DNS
dig example.com MX
dig example.com TXT
dig _dmarc.example.com TXT
dig selector1._domainkey.example.com TXT

# DNSBL / Blacklist check (reverse IP octets)
dig 2.0.0.127.bl.spamcop.net A +short
dig 2.0.0.127.dnsbl.sorbs.net A +short
FAQ
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Is this DNS tool free?
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Yes. It is free to use and runs in the browser.
Does this page show true global propagation?
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No single web page can show the state of every recursive resolver on the internet. This tool compares public resolvers so you can see real answer differences without pretending they represent every network.
Can I use this to check email DNS records?
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Yes. The mail DNS module helps inspect MX, SPF, DMARC, and optional DKIM selector lookups from one place.
Does OpsKit store my DNS lookups?
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This page is designed to run without a server-side DNS proxy and without localStorage. Public DNS providers still receive the queries because the browser talks to them directly.
Can I check if my IP is blacklisted?
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Yes. The Blacklist tab checks your IPv4 address against 7 open DNSBLs including SpamCop, SORBS, and CBL. Use 127.0.0.2 as a test IP — most DNSBLs return a positive result for that address.
Where should I go for advanced DNS incident workflows?
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Use DNS Ops Lab when you need deeper resolver comparison, cutover planning, negative-cache investigation, or alias tracing.
Related Tools#
  • DNS Ops Lab - advanced DNS troubleshooting workflows
  • SSL Tools - certificate and chain debugging for hostnames you resolve
  • PromQL Studio - build operational queries once DNS and endpoints are sorted
  • kubectl Builder - generate Kubernetes commands during service and ingress investigations