Detecting browser extensions for bot detection, lessons from LinkedIn and Castle

This article analyzes browser extension detection techniques for bot and fraud detection, detailing LinkedIn’s approach of probing web-accessible extension resources via chrome-extension URLs and its tradeoffs (console noise, observability, performance), and contrasting it with Castle’s quieter method that identifies extensions through DOM and JavaScript side effects (e.g., injected elements, globals). It concludes that extension detection is a contextual, weak signal on its own but valuable when combined with broader fingerprinting and behavioral indicators.