WebXR is a cross-platform Web API for augmented reality (AR) and virtual reality (VR). We have released the WebXR Viewer to give web developers a chance to experiment with web-based AR experiences on iOS using WebXR, and provide a way for us to get feedback for the WebXR community as it continues to develop AR support in the WebXR specification. The WebXR viewer implements a collection of accepted and proposed WebXR AR API features, and also supports some of the non-standard features we developed for an early version of the WebXR API. Version 2 of the WebXR Viewer is based on the Firefox for iOS source code, so is a much more full-featured web browser. Some of Firefox's features are working (e.g., account sync), while some features are still in development (e.g., send-to-device). Please report problems or feature requests as issues at https://github.com/mozilla-mobile/webxr-ios-js To learn more about the WebXR Viewer and other ways Mozilla is working with the web community to bring augmented reality, virtual reality and mixed reality to the web, visit https://mixedreality.mozilla.org/