Apple this week released Safari Technology Preview 54 for macOS Sierra and macOS High Sierra and it contains updates for Web APIs and WebRTC.
Safari Technology Preview 54 contains a fix for the Clipboard API related to copying a list from Microsoft Word to TinyMCE as well as an update that prioritizes file promises over filenames when performing drag and drop actions. The implementation of the Beacon API contains a fix for validating redirect responses against CORS. And the Web API now supports the createImageBitmap method.
The technology preview also contains improvements to WebRTC. Specifically, Apple has added a special software encoder mode for when a compression session is not using a hardware encoder and VCP is not active. It also added experimental support for two MDNS Interactive Connectivity Establishment (ICE) candidates, which are involved in WebRTC signaling.
Safari Technology Preview 54 is available for download here.