A web browser is software used to view web content and run browser-based applications. It renders pages, executes JavaScript, manages cookies and sessions, and often hosts plugins, extensions, and web apps inside a sandboxed environment. When a tool is delivered through the browser, it can be used immediately without installation, which is why browsers are a common delivery path for modern software.
In cybersecurity, the browser is a high-value attack surface because it processes untrusted content from the internet. Attackers use phishing pages, malicious scripts, drive-by downloads, and compromised extensions to steal credentials or run unwanted code. Defenders reduce risk with rapid patching, sandboxing, site isolation, extension controls, content filtering, and cautious handling of links and downloads. In practice, the browser is both a gateway to services and a place where trust must be tightly managed.