Browser traffic is the stream of requests and responses a web browser sends and receives while loading sites and services. It includes page fetches, API calls, redirects, cookies, scripts, images, and file downloads. Much of it travels over HTTPS, but the browser still decides what to request and how to handle the replies, which makes this traffic a key control point.
In cyber security, browser traffic matters because it can reveal or enable malicious behavior. Phishing pages, adware, tracking scripts, malicious extensions, and proxy-based tools may redirect, inspect, or relay this traffic. Defenders watch browser traffic for unusual destinations, unexpected requests, login theft, data exfiltration, or signs that a browser is being used as a network relay. Security controls such as browser hardening, extension review, secure web gateways, and DNS or proxy monitoring help detect abuse before ordinary web activity turns into a covert channel.