Discovery Tools
Use discovery tools when you are mapping an environment, finding related services, or gathering clues before a deeper DNS or email investigation.
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Start With The Right Tool
Find Related Hostnames
Start here when you need to enumerate likely subdomains or understand the wider hostname footprint of a domain.
Identify Hosted Services
Use DNS patterns and certificate clues to infer what platforms or providers are probably in use.
Look For DKIM Selectors
If you are validating mail setup and do not know the selector yet, start with a selector-focused discovery path.
Featured Tools
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Discovery
Subdomain Finder
Search certificate transparency data for related hostnames.
Hosted Service Fingerprint Finder
Identify likely hosted platforms and services from DNS clues.
Certificate SAN Explorer
Fetch a TLS certificate and list its SAN hostnames.
DKIM Selector Finder
Try common selectors and discover likely DKIM records.
Featured Articles
What Is a Dangling CNAME?
Learn what a dangling CNAME is, why it can create subdomain takeover risk, what patterns to look for, and how to clean up stale aliases safely.
What Is an SRV Record in DNS?
Learn what an SRV record is, how service, protocol, priority, weight, and port fields work, and when SRV lookups are useful in real deployments.
Common Glue Record Problems: DNS Delegation Issues Explained
A troubleshooting guide to glue record issues, including in-bailiwick nameservers, missing glue, delegation mismatches, and how to fix DNS resolution failures.
Common PTR Record Problems: Reverse DNS Issues Explained
A practical guide to PTR record problems, including missing reverse DNS, forward-confirmed reverse DNS, hostname issues, and how PTR impacts email deliverability.
How to Check DKIM Selectors (Step-by-Step Guide)
Learn how to find and check DKIM selectors, query DNS correctly, and troubleshoot missing or invalid DKIM records with real examples.
How to Check DNS Propagation (Step-by-Step Guide)
A practical step-by-step guide to checking DNS propagation, including what to compare, how TTL affects results, and how to interpret inconsistent answers.