Release Notes for Safari Technology Preview 29

Safari Technology Preview Release 29 is now available for download for macOS 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 215271-215859.


  • Implemented Intl.DateTimeFormat.prototype.formatToParts (r215616)
  • Improved Date.parse to accept wider range of date strings (r215359)
  • Implemented Object.isFrozen() and Object.isSealed() according to ECMA specifications (r215272)


  • Added support for percentage gaps for CSS Grid (r215463)
  • Changed :focus-within behavior to match specifications (r215719)


  • Avoided repaints for invisible animations on (r215507)
  • Fixed rendering flexbox children across columns (r215320)
  • Fixed text-align:start and text-align:end behavior in table cells (r215375)
  • Fixed animations with large negative animation-delays that fail depending on machine uptime (r215352)
  • Reduced redundant text measuring during mid-word breaking (r215666)
  • Changed memory handling to keep all of the decoded frames for an animated image if the total memory size of the frames is under 30MB (up from 5MB) (r215557)
  • Fixed <li> content inside <ul> to wrap mid-word when word-break:break-word is set (r215660)
  • Fixed the location of the “recent searches” popover of <input type="search"> in RTL mode (r215830)

Web Inspector

  • Added regular expression support to XHR breakpoints (r215584)
  • Added a pause reason for “All Requests” XHR breakpoint (r215427)
  • Fixed the enabled state of “All Requests” XHR breakpoint to be correctly restored (r215435)
  • Fixed a bug where XHR breakpoints would disappear when the inspected page is reloaded (r215473)
  • Fixed XHR breakpoints restored from settings but not appearing in the sidebar (r215422)
  • Fixed Network datagrid columns to correctly restore their shown or hidden state (r215449)
  • Added tooltips to Network grid items for easier reading when text overflows (r215631)
  • Fixed sorting by Priority column in Network datagrids (r215793)
  • Fixed the display of Web Socket messages with non-latin letters (r215388)
  • Prevented showing the Search tab for location links, prefer the Resources tab (r215630)
  • Changed to treat Uint8ClampedArray as an array, not an object (r215855)
  • Fixed Command-G (⌘G) shortcut to allow Find next to work in the console (r215795)
  • Implemented autocompletion for CSS variables (r215358)
  • Updated the icon for the Ignore resource cache button in the Network Tab (r215440)


  • Added support for ECDSA (r215423)
  • Improved converting an ECDSA signature binary into DER format (r215791)


  • Changed the role description of <hr> from “separator” to “rule” (r215532)


  • Restricted WebKit image formats to a known whitelist (r215706, r215829). WebKit now only loads images of the following formats:
    • PNG (.png)
    • GIF (.gif)
    • JPEG (.jpg), (.jpeg), (.jpe), (.jif), (.jfif), (.jfi)
    • JPEG 2000 (.jp2), (.j2k), (.jpf), (.jpx), (.jpm), (.mj2)
    • TIFF (.tiff), (.tif)
    • MPO (.mpo)
    • Microsoft Bitmap (.bmp), (.dib)
    • Microsoft Cursor (.cur)
    • Microsoft Icon (.ico)

Bug Fixes

  • Fixed an issue where the status bar would not display modifier key information (e.g. “Open * in new tab” when holding the Command key) (r215790)
  • Improved performance of typing on pages with many <input> elements
  • Fixed an issue where a hardware “enter” key would not dismiss JavaScript alert, confirm, or prompt; previously, only the “return” key would dismiss a dialog
  • Fixed QuotaExceededError when saving to localStorage in private browsing mode or WebDriver sessions (r215315)
  • Fixed an issue where the Content-Disposition header filename was ignored when the download attribute is specified (r215736)
  • Fixed escaping ‘<‘ and ‘>’ in attribute values when using XMLSerializer.serializeToString() API (r215648)
  • Fixed issues causing beforeunload dialog to be shown even though the user did not interact with the page (r215404)
  • Changed all CORS requests and cross origin access from file:// to be blocked unless Disable Local File Restrictions is selected from the Develop menu