theHarvester is an open-source OSINT (Open-Source Intelligence) tool written in Python, pre-installed on Kali Linux designed for gathering publicly available information about a target domain or company. It collects data such as email addresses, subdomains, virtual hosts, open ports, banners, and employee names from sources like search engines (e.g., DuckDuckGo, Bing), Shodan, and breach databases. With a modular architecture, it supports over 30 data sources, including Censys, VirusTotal, and crt.sh, enabling efficient reconnaissance for penetration testing and cybersecurity research. Features include DNS brute-forcing, API endpoint scanning, screenshot capture, and JSON/XML output for reporting. Maintained by Christian Martorella theHarvester is ideal for ethical hackers and security analysts, offering a lightweight, command-line interface with RESTful API support via restfulHarvest.