The Complete Guide to Online Reverse DNS and IP Lookup Tools

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As an IT professional, I often need to look up DNS and IP address details for security research and troubleshooting network issues. Reverse DNS and IP lookups are invaluable techniques for any tech geek‘s toolkit.

In this comprehensive guide, I‘ll explain these lookup processes in-depth and explore powerful tools to perform them yourself. Whether you‘re an aspiring hacker or seasoned sysadmin, read on for an insider‘s perspective on getting the most out of online DNS and IP lookups!

DNS Lookups: Mapping Domains to IP Addresses

First, let‘s quickly review how standard DNS lookups work.

The Domain Name System (DNS) is like the phonebook of the internet – it translates human-readable domain names into machine-readable IP addresses. This process is known as forward DNS resolution.

For example, when you type into your browser, a DNS lookup resolves it to the IP address This allows your computer to route your request to the correct server.

According to Cloudflare, DNS lookups are powered by A records, which map domains to IPs. All websites rely on DNS to route traffic properly.

Now let‘s flip things around…

Reverse DNS Lookups: Revealing Domains Mapped to IPs

A reverse DNS (rDNS) lookup works backwards – starting with an IP address and checking which domains are associated with it.

Reverse DNS can tell you all the DNS A records pointing to a given IP. For example, a reverse lookup on would reveal and any other domains hosted on that server.

According to Imperva, shared hosting environments with multiple sites on one server are common targets for reverse DNS lookups. Hackers can use them to uncover other attack surfaces if their initial target proves difficult to penetrate.

But reverse lookups are also hugely useful for legitimate IT troubleshooting. As a systems administrator, I rely on them to investigate connectivity issues and identify shared assets.

Now let‘s dive into some excellent online reverse lookup tools that make gathering intel a breeze!

WhoisXML API: Robust Historical Reverse DNS Data

My personal favorite is WhoisXML API, which offers enterprise-grade DNS and IP lookup capabilities.

According to WhoisXML API, their database contains billions of historical DNS records collected through passive monitoring of global DNS traffic. This enormous dataset provides unmatched visibility into current and past DNS mappings.

WhoisXML API Reverse DNS Lookup Tool

As a geek, I‘m really impressed by the sheer scale of their DNS intelligence. Some key stats:

  • 11 billion historical DNS records
  • Over 300 million domain names
  • 185 million unique IPs
  • Lookups across 230+ TLDs

Source: WhoisXML API Product Page

WhoisXML API offers multiple ways to access this data:

  • API – Up to 10 automated lookups/second in XML/JSON
  • Database – Bulk CSV downloads updated daily to monthly
  • Lookup Tool – Instant results right in your browser

The API is handy for integrating reverse DNS directly into other tools and workflows. For example, you can build a custom dashboard or automate threat intelligence gathering in Splunk.

For casual browsing, I like using their lookup GUI which is free up to 100 queries/month. Simply enter a domain or IP, click search, and immediately see all associated DNS info.

Having this historical DNS context enables all sorts of use cases:

  • Enrich threat intelligence platforms
  • Accelerate incident response
  • Expose hidden connections
  • Uncover DNS anomalies
  • Identify shared infrastructure for security audits

Overall, I highly recommend WhoisXML API for comprehensive reverse DNS data. The breadth of information and lookup flexibility is unparalleled. Quick and Easy Lookups

If you just need a fast and free lookup from time to time, check out

ViewDNS has a straightforward lookup box where you enter a domain or IP address and it shows you the reverse mappings. It‘s perfect for quick occasional browsing.

ViewDNS Reverse Lookup Page

Some other handy ViewDNS tools include:

  • Reverse WHOIS lookups
  • Blacklist checks
  • DNS report generation

ViewDNS also has shared DNS checking to see what other websites use the same nameservers. This can uncover infrastructural relationships that reverse DNS lookups miss.

Overall, ViewDNS is easy to use with a clean interface. Just don‘t expect the most comprehensive results – its database isn‘t nearly as robust as some paid alternatives. But for free ad-hoc lookups, ViewDNS gets the job done nicely.

HackerTarget: Infosec Pro Toolbox

If you‘re an IT pro or security researcher, check out HackerTarget. This Australia-based platform offers a suite of intel gathering and reconnaissance tools.

HackerTarget Reverse IP Lookup

HackerTarget provides the essentials like reverse DNS, WHOIS, and ping lookups. But it also has advanced capabilities like port scanning, page scraping, infrastructure mapping, and more.

I especially like their subdomain scanner which helps uncover a website‘s entire scope quickly. Finding all subdomains is crucial for penetration testing and attack surface mapping.

HackerTarget offers a clean interface, fast performance, and excellent uptime. Their tools are simple yet powerful. It‘s a great platform for IT pros doing hands-on security research and testing.

MXToolbox: Focused on Core DNS Tools

MXToolbox is targeted squarely at email admins with an emphasis on core DNS and mail server tools.

As the name suggests, MXToolbox started out focused on MX record lookups for email routing. They‘ve expanded to other handy DNS tools like reverse lookups.

MXToolbox Reverse Lookup Page

To do a reverse lookup, just enter an IP address and hit Lookup. MXToolbox checks its (smaller) database and displays associated domains.

Some other useful MXToolbox tools include:

  • Blacklist monitoring
  • DNS health checks
  • SPF and DMARC lookups

MXToolbox lacks some advanced capabilities found in larger suites like HackerTarget. However, the tools it does provide are simple and reliable. For email geeks like myself, it‘s a handy bookmark to have around.

Command Line Lookup with Crips (For Linux Gurus)

Finally, I want to showcase a cool reverse DNS lookup tool that runs right in your Linux terminal. Meet Crips!

Crips is an open-source toolkit containing various DNS and IP lookup utilities. It lets geeks like me perform lookups without ever leaving my command line.

Crips Reverse IP Lookup Tool

To install Crips:

git clone
cd Crips  

Once running, choose option 7 for a reverse IP lookup. Enter your target IP or domain, and Crips will display results right in your terminal.

It‘s a handy way to get quick DNS answers without using your mouse or browser. The command line flows fast once you get used to it!

The Takeaway: Reverse DNS Is a Must-Have Skill

Being able to leverage DNS and IP lookup tools is an invaluable skill for any IT professional or cybersecurity geek. Here are my key takeaways:

  • Quick lookups – ViewDNS and MXToolbox for simple searches
  • Large-scale data – WhoisXML API for advanced historical lookups
  • Security testing – HackerTarget for infosec pros
  • Email sysadmins – MXToolbox‘s mail server tools
  • Command line gurus – Crips for terminal-based lookups

With so many options, you can choose the right tool for each situation. Properly utilizing reverse DNS and IP lookups enables all kinds of use cases:

  • Investigating network issues
  • Security research and recon
  • Uncovering hidden infrastructure
  • Enriching threat intelligence
  • Accelerating incident response

I highly recommend getting familiar with these lookup processes. They provide invaluable insight into the hidden relationships and interconnections on networks and the internet.

Hopefully this guide has sparked some ideas on how you can incorporate reverse DNS and IP lookups into your own IT or infosec activities! Let me know if you have any other favorite lookup tools I should check out.

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