# Safari Technology Preview 55 Release Notes Preview the latest web technology updates including: CSS, Web API, Rendering, Accessibility, JavaScript, Web Driver, Web Inspector, Media, WebRTC, Security, and Bug Fixes. ## Overview [Safari Technology Preview](https://webkit.org/blog/6017/introducing-safari-technology-preview/) Release 55 is now [available for download](https://webkit.org/downloads/) for macOS Sierra and macOS High Sierra. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab. This release covers WebKit revisions [230521-230913](https://trac.webkit.org/log?stop_rev=230521&rev=230913&limit=999). ### CSS - Added support for `calc()` in `webkit-gradient` and `cross-fade` ([r230816](https://trac.webkit.org/changeset/230816/webkit/)) - Changed `:active` pseudo class to deactivate when using pressure sensitive trackpad ([r230786](https://trac.webkit.org/changeset/230786/webkit/)) - Omitted the default value when serializing `font-feature-settings` ([r230838](https://trac.webkit.org/changeset/230838/webkit/)) - Updated HSL and HSLA parsing to match CSS Color 4 ([r230861](https://trac.webkit.org/changeset/230861/webkit/)) ### Web API - Enforced `content-type` for `