A subdomain is a prefix added to a domain name, separated by a dot (e.g. blog.example.com, api.example.com). Subdomains are used to organize different sections or services of a website.

How does this tool find subdomains?

This tool probes a list of common subdomain prefixes (www, mail, api, blog, dev, etc.) using Google Public DNS. If a DNS A record exists for a subdomain, it is considered active.

Will this find all subdomains?

No. It only checks a predefined list of common prefixes. To find all subdomains, you need certificate transparency logs, DNS brute-forcing, or zone transfer access — none of which are available in a free browser tool.

Is it safe to use this on any domain?

DNS lookups are read-only and do not affect the target domain. You should only use this tool on domains you own or have permission to test. Never use subdomain enumeration tools for unauthorized reconnaissance.

Does this perform a complete subdomain enumeration?

No. The tool probes a list of common subdomain names — it does not perform brute-force or full DNS zone transfer enumeration. It finds the most common public subdomains quickly.

Is it legal to scan another domain's subdomains?

Querying public DNS records is legal and is how the internet works. The tool only performs DNS lookups (no port scanning or exploitation). Always ensure you have authorization before security testing any infrastructure.

Subdomain Finder — Discover Subdomains of Any Domain Free

Discover active subdomains for any domain by probing common prefixes via DNS. See IP addresses for each found subdomain. Free, instant.

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This tool probes 38 common subdomain prefixes using Google Public DNS. It does not perform brute-force enumeration or zone transfer attacks. Use only on domains you own or have permission to test.

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What is Subdomain Finder — Find Active Subdomains Free?

A subdomain finder probes a domain for common subdomain prefixes (www, mail, blog, api, dev, staging, app, cdn, etc.) using DNS lookups. It returns all subdomains that resolve to a valid IP address, revealing the visible attack surface, server infrastructure, and service topology of any domain. Used by web developers, security researchers, and SEO professionals.

How to Use Subdomain Finder — Find Active Subdomains Free

1Enter the root domain you want to probe (e.g., example.com).
2Click Find Subdomains to start the DNS probe.
3Review each found subdomain and its resolved IP address.
4Note any unexpected subdomains that may need attention.

Key Features

Probes 100+ common subdomain prefixes
Shows resolved IP for each active subdomain
Detects www, mail, blog, api, dev, staging, and more
Fast parallel DNS lookups
Free with no sign-up

Benefits

Map your own domain's subdomain structure
Audit staging and dev subdomains exposed to the internet
Research competitor infrastructure
Security reconnaissance for authorized penetration testing

Why Use Irreva for Subdomain Finder — Find Active Subdomains Free?

Map your own domain's subdomain structure

Audit staging and dev subdomains exposed to the internet

Research competitor infrastructure

Runs 100% in your browser — files never leave your device.

No account, no sign-up, no subscription — free forever.

Works on any device: desktop, tablet, or mobile.

Frequently Asked Questions

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