WhatWeb is an open-source web technology fingerprinting tool that identifies the technologies used by websites. It analyzes HTTP responses, HTML content, headers, cookies, and other fingerprints to detect content management systems (CMS), web servers, JavaScript libraries, frameworks, analytics services, security technologies, and more.
With over 1,800 detection plugins, WhatWeb can also identify software versions, email addresses, account IDs, SQL errors, web framework modules, and other valuable information useful during the reconnaissance phase of penetration testing.
The primary purpose of WhatWeb is to identify and fingerprint the technologies powering a website. It helps security professionals gather technical information about a target, enabling them to identify potential attack surfaces before conducting further assessment or exploitation.