Browser extension scrapers (built with the WebExtensions API) execute JavaScript inside the browser process, with full access to cookies, authenticated sessions, and the rendered DOM. Because they are indistinguishable from user-initiated code, they bypass most anti-bot fingerprinting checks that target headless environments.
Extension-based scrapers are useful for sites that are extremely difficult to access programmatically — financial portals, enterprise SaaS dashboards, and sites with sophisticated bot protection that defeats headless browsers. The user navigates to the target page normally; the extension reads the DOM and exports the data.
Limitations include: manual trigger (not fully automated), single-threaded execution, and the need for the user's browser to be open. Extensions cannot be scaled beyond a single user session, making them suitable for low-volume or one-time data collection rather than production scraping pipelines.