subfinder is a subdomain discovery tool that discovers valid subdomains for websites by using passive online sources. It has a simple modular architecture and is optimized for speed. subfinder is built for doing one thing only - passive subdomain enumeration, and it does that very well.

We have designed subfinder to comply with all passive sources licenses, and usage restrictions, as well as maintained a consistently passive model to make it useful to both penetration testers and bug bounty hunters alike.

Resources

• Features
• Usage
• Installation Instuctions (direct)
• Installation Instructions
  • From Binary
  • From Source
  • From Github
• Upgrading
• Post Installation Instructions
• Running subfinder
• Running in a Docker Container

Features

• Simple and modular code base making it easy to contribute.
• Fast And Powerful Resolution and wildcard elimination module
• Curated passive sources to maximize results (35 Sources as of now)
• Multiple Output formats supported (Json, File, Stdout)
• Optimized for speed, very fast and lightweight on resources
• Stdin and stdout support for integrating in workflows

Usage

subfinder -h

This will display help for the tool. Here are all the switches it supports.

Flag	Description	Example
-all	Use all sources (slow) for enumeration	subfinder -d uber.com -all
-cd	Upload results to the Chaos API (api-key required)	subfinder -d uber.com -cd
-config string	Configuration file for API Keys, etc	subfinder -config config.yaml
-d	Domain to find subdomains for	subfinder -d uber.com
-dL	File containing list of domains to enumerate	subfinder -dL hackerone-hosts.txt
-exclude-sources	List of sources to exclude from enumeration	subfinder -exclude-sources archiveis
-max-time	Minutes to wait for enumeration results (default 10)	subfinder -max-time 1
-nC	Don't Use colors in output	subfinder -nC
-nW	Remove Wildcard & Dead Subdomains from output	subfinder -nW
-ls	List all available sources	subfinder -ls
-o	File to write output to (optional)	subfinder -o output.txt
-oD	Directory to write enumeration results to (optional)	subfinder -oD ~/outputs
-oI	Write output in Host,IP format	subfinder -oI
-oJ	Write output in JSON lines Format	subfinder -oJ
-r	Comma-separated list of resolvers to use	subfinder -r 1.1.1.1,1.0.0.1
-rL	Text file containing list of resolvers to use	subfinder -rL resolvers.txt
-recursive	Enumeration recursive subdomains	subfinder -d news.yahoo.com -recursive
-silent	Show only subdomains in output	subfinder -silent
-sources	Comma separated list of sources to use	subfinder -sources shodan,censys
-t	Number of concurrent goroutines for resolving (default 10)	subfinder -t 100
-timeout	Seconds to wait before timing out (default 30)	subfinder -timeout 30
-v	Show Verbose output	subfinder -v
-version	Show current program version	subfinder -version

Installation Instructions

From Binary

The installation is easy. You can download the pre-built binaries for different platforms from the releases page. Extract them using tar, move it to your $PATH and you're ready to go.

▶ # download release from https://github.com/projectdiscovery/subfinder/releases/
▶ tar -xzvf subfinder-linux-amd64.tar.gz
▶ mv subfinder /usr/local/bin/
▶ subfinder -h

From Source

subfinder requires go1.14+ to install successfully. Run the following command to get the repo -

GO111MODULE=on go get -u -v github.com/projectdiscovery/subfinder/v2/cmd/subfinder

From Github

git clone https://github.com/projectdiscovery/subfinder.git
cd subfinder/v2/cmd/subfinder
go build .
mv subfinder /usr/local/bin/
subfinder -h

Post Installation Instructions

Subfinder will work after using the installation instructions however to configure Subfinder to work with certain services, you will need to have setup API keys. The following services do not work without an API key:

• Binaryedge
• Certspotter
• Censys
• Chaos
• DnsDB
• Github
• Intelx
• Passivetotal
• Recon.dev
• Robtex
• SecurityTrails
• Shodan
• Spyse
• Threatbook
• Virustotal
• Zoomeye

Theses values are stored in the $HOME/.config/subfinder/config.yaml file which will be created when you run the tool for the first time. The configuration file uses the YAML format. Multiple API keys can be specified for each of these services from which one of them will be used for enumeration.

For sources that require multiple keys, namely Censys, Passivetotal, they can be added by separating them via a colon (:).

An example config file -

resolvers:
  - 1.1.1.1
  - 1.0.0.1
sources:
  - binaryedge
  - bufferover
  - censys
  - passivetotal
  - sitedossier
binaryedge:
  - 0bf8919b-aab9-42e4-9574-d3b639324597
  - ac244e2f-b635-4581-878a-33f4e79a2c13
censys:
  - ac244e2f-b635-4581-878a-33f4e79a2c13:dd510d6e-1b6e-4655-83f6-f347b363def9
certspotter: []
passivetotal:
  - sample-email@user.com:sample_password
securitytrails: []
shodan:
  - AAAAClP1bJJSRMEYJazgwhJKrggRwKA
github:
  - d23a554bbc1aabb208c9acfbd2dd41ce7fc9db39
  - asdsd54bbc1aabb208c9acfbd2dd41ce7fc9db39

Running Subfinder

To run the tool on a target, just use the following command.

▶ subfinder -d freelancer.com

This will run the tool against freelancer.com. There are a number of configuration options that you can pass along with this command. The verbose switch (-v) can be used to display verbose information.

[threatcrowd] ns1.hosting.freelancer.com
[threatcrowd] ns2.hosting.freelancer.com
[threatcrowd] flash.freelancer.com
[threatcrowd] auth.freelancer.com
[chaos] alertmanager.accounts.freelancer.com
[chaos] analytics01.freelancer.com
[chaos] apidocs.freelancer.com
[chaos] brains.freelancer.com
[chaos] consul.accounts.freelancer.com

The -silent switch can be used to show only subdomains found without any other info.

The -o command can be used to specify an output file.

▶ subfinder -d freelancer.com -o output.txt

To run the tool on a list of domains, -dL option can be used. This requires a directory to write the output files. Subdomains for each domain from the list are written in a text file in the directory specified by the -oD flag with their name being the domain name.

▶ cat domains.txt
hackerone.com
google.com

▶ subfinder -dL domains.txt -oD ~/path/to/output
▶ ls ~/path/to/output

hackerone.com.txt
google.com.txt

You can also get output in json format using -oJ switch. This switch saves the output in the JSON lines format.

If you use the JSON format, or the Host:IP format, then it becomes mandatory for you to use the -nW format as resolving is essential for these output format. By default, resolving the found subdomains is disabled.

▶ subfinder -d hackerone.com -o output.json -oJ -nW
▶ cat output.json

{"host":"www.hackerone.com","ip":"104.16.99.52"}
{"host":"mta-sts.hackerone.com","ip":"185.199.108.153"}
{"host":"hackerone.com","ip":"104.16.100.52"}
{"host":"mta-sts.managed.hackerone.com","ip":"185.199.110.153"}

The new highlight of this release is the addition of stdin/stdout features. Now, domains can be piped to subfinder and enumeration can be ran on them. For example -

▶ echo hackerone.com | subfinder
▶ cat targets.txt | subfinder

The subdomains discovered can be piped to other tools too. For example, you can pipe the subdomains discovered by subfinder to httpx httpx which will then find running http servers on the host.

▶ echo hackerone.com | subfinder -silent | httpx -silent

http://hackerone.com
http://www.hackerone.com
http://docs.hackerone.com
http://api.hackerone.com
https://docs.hackerone.com
http://mta-sts.managed.hackerone.com

Running in a Docker Container

You can use the official dockerhub image at subfinder. Simply run -

▶ docker pull projectdiscovery/subfinder

The above command will pull the latest tagged release from the dockerhub repository.

If you want to build the container yourself manually, git clone the repo, then build and run the following commands

• Clone the repo using git clone https://github.com/projectdiscovery/subfinder.git
• Build your docker container

docker build -t projectdiscovery/subfinder .

• After building the container using either way, run the following -

docker run -it projectdiscovery/subfinder

▶ The above command is the same as running -h

If you are using docker, you need to first create your directory structure holding subfinder configuration file. After modifying the default config.yaml file, you can run:

▶ mkdir -p $HOME/.config/subfinder
▶ cp config.yaml $HOME/.config/subfinder/config.yaml
▶ nano $HOME/.config/subfinder/config.yaml

After that, you can pass it as a volume using the following sample command.

▶ docker run -v $HOME/.config/subfinder:/root/.config/subfinder -it projectdiscovery/subfinder -d freelancer.com

For example, this runs the tool against uber.com and output the results to your host file system:

docker run -v $HOME/.config/subfinder:/root/.config/subfinder -it projectdiscovery/subfinder -d uber.com > uber.com.txt

License

subfinder is made with 🖤 by the projectdiscovery team. Community contributions have made the project what it is. See the Thanks.md file for more details.

Read the disclaimer for usage at DISCLAIMER.md and contact us for any API removal.