Lea Verou makes case for polyfills as a driver of web standards progress

Web developer and standards advocate Lea Verou has published a post defending polyfills as a net positive for the web platform, directly responding to WHATWG spec editor Anne van Kesteren, who argued at a recent WHATWG meeting that polyfilling is harmful. Van Kesteren had expressed a preference for libraries that demonstrate developer need rather than tools that mimic proposed API shapes and constrain design flexibility. Verou contends that polyfills decouple API design from implementation, reducing complexity and allowing authors to write against standardised surfaces before browsers ship native support. She points to historical examples such as IE7.js and html5shiv as evidence that polyfills enabled web progress during the IE era, and argues that a widely adopted polyfill is a consequence of unmet developer need, not its cause. Verou also notes that native implementations tend to be more performant, accessible, and internationalisation-friendly than userland alternatives, framing polyfills as demand signals that ultimately drive implementor interest.