subfinder

Subfinder is a command-line tool designed for discovering subdomains of a given domain. It is written in Go language and provides a fast and efficient way of finding subdomains. With its simple interface, it allows users to easily identify potential attack vectors and gather information about a target domain.

Subfinder uses multiple public and private APIs to perform its scans, ensuring a wide coverage of subdomains. It has a built-in rate limiter to prevent abuse and avoid excessive queries that might result in getting blocked by the target domain's infrastructure.

The tool organizes the results in different formats, including CSV, JSON, and textual output. This enables seamless integration with other tools and further analysis by security professionals. It also has features like filtering and wildcard enumeration to refine the search and focus on specific subdomains of interest.

Subfinder supports a variety of flag options that allow customization of the scanning process. Users can specify the number of threads to use, specify a wordlist for brute-forcing subdomains, and even use it as a library in their own Go programs.

Overall, Subfinder is a versatile and powerful tool that helps security researchers, penetration testers, and bug bounty hunters in discovering subdomains and identifying potential vulnerabilities in target domains.