---
title: Safari Technology Preview 166 Release Notes
framework: safari-technology-preview-release-notes
role: article
role_heading: Article
path: safari-technology-preview-release-notes/stp-release-166
---

# Safari Technology Preview 166 Release Notes

Learn about the latest web technology updates in Safari Technology Preview: Web Inspector, CSS, JavaScript, Popover, Media, MSE, Web API, and Accessibility.

## Overview

Overview Safari Technology Preview Release 166 is now available for download for macOS Monterey 12.3 or later and macOS Ventura. If you already have Safari Technology Preview installed, you can update it in the Software Update pane of System Preferences on macOS Monterey, or System Settings under General → Software Update on macOS Ventura. This release includes WebKit changes between: 260849@main…261247@main. Web Inspector Added input fields for editing variation axes values in Fonts sidebar panel (261162@main) CSS Enabled @counter-style by default (261182@main, 260912@main, 261135@main) Enabled CSS contain-intrinsic-size by default (261185@main) Fixed serialization of image-set() to use authored order (261015@main) Implemented @supports with the & nesting operator (261004@main) Implemented text-transform: full-width (261211@main) Fixed floats trimmed margins to not contribute to the containing block’s intrinsic sizing (260906@main) JavaScript Implemented RegExp v flag with set notation and properties of strings (261188@main) Enabled new WASM baseline JIT (BBQ) for increased performance (261153@main) Inlined Proxy [[Set]] trap in DFG / FTL (261058@main) Made C++ to JS calls faster (260858@main) Popover Enabled the popover attribute (261193@main) Implemented [popover=auto] and light dismiss behavior (261093@main) Media Fixed picture-in-picture video snapping to incorrect size (261383@main) MSE Changed to only fire durationchange after parsing the media buffer (261029@main) Web API Added support for preconnect via HTTP early hints (261079@main) Added Cancel, Unknown, and Clear keycodes (261008@main) Added selection API that works across shadow boundaries (261021@main) Added support for largeBlob extension for the local authenticator (260958@main) Adjusted text input scrollWidth and scrollHeight to include padding and any whitespace added by decorations (261121@main) Fixed translation for shadow DOM content (261096@main) Fixed translation to treat a floating list item as its own paragraph (261114@main) Fixed Speech Recognition API terminating after one utterance or a short time (260886@main) Fixed window.onload getting repeatedly re-executed when changing the URL fragment during onload (260860@main) Improved support for prioritized HTTPS navigations (261022@main) Stripped tab and newline from Location, URL, <a>, and <area>’s protocol setter (261017@main) Accessibility Fixed input[type=date] individual fields getting announced as “group” (261123@main) Fixed the wrong role displayed for input in Web Inspector (260868@main)

## See Also

### 2023

- [Safari Technology Preview 185 Release Notes](safari-technology-preview-release-notes/stp-release-185.md)
- [Safari Technology Preview 184 Release Notes](safari-technology-preview-release-notes/stp-release-184.md)
- [Safari Technology Preview 183 Release Notes](safari-technology-preview-release-notes/stp-release-183.md)
- [Safari Technology Preview 182 Release Notes](safari-technology-preview-release-notes/stp-release-182.md)
- [Safari Technology Preview 181 Release Notes](safari-technology-preview-release-notes/stp-release-181.md)
- [Safari Technology Preview 180 Release Notes](safari-technology-preview-release-notes/stp-release-180.md)
- [Safari Technology Preview 179 Release Notes](safari-technology-preview-release-notes/stp-release-179.md)
- [Safari Technology Preview 178 Release Notes](safari-technology-preview-release-notes/stp-release-178.md)
- [Safari Technology Preview 177 Release Notes](safari-technology-preview-release-notes/stp-release-177.md)
- [Safari Technology Preview 176 Release Notes](safari-technology-preview-release-notes/stp-release-176.md)
- [Safari Technology Preview 175 Release Notes](safari-technology-preview-release-notes/stp-release-175.md)
- [Safari Technology Preview 174 Release Notes](safari-technology-preview-release-notes/stp-release-174.md)
- [Safari Technology Preview 173 Release Notes](safari-technology-preview-release-notes/stp-release-173.md)
- [Safari Technology Preview 172 Release Notes](safari-technology-preview-release-notes/stp-release-172.md)
- [Safari Technology Preview 171 Release Notes](safari-technology-preview-release-notes/stp-release-171.md)