CSS Scoping

In plain words: Shadow DOM v1 is a core web standard that allows developers to attach a hidden, encapsulated DOM tree to a host element. By isolating the component's internal markup, styles, and scripts from the rest of the web page, Shadow DOM prevents global CSS leakage and script conflicts, making it the foundational engine behind modern frameworks like Salesforce LWC. In modern web development, building robust and maintainable web applications requires strict component encapsulation. Without isolation, global CSS rules often collide, causing unexpected layout shifts across components. Shadow DOM v1 solves this problem by providing native browser-level encapsulation for reusable custom elements.