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# Safari Technology Preview 1 Release Notes

Preview the latest web technology updates including: browser differences, JavaScript improvements, HTML enhancements, and Web Inspector changes.

## Overview

Safari Technology Preview is available as a download for macOS Sierra and OS X El Capitan. If you already have Safari Technology Preview installed, you can update from the [Mac App Store’s Updates tab](macappstore://showUpdatesPage).

### Browser Differences

- Safari Technology Preview can be run side-by-side with Safari and set as the default browser
- Separate local data stores are used for history, bookmarks, cookies, and cache
- Browsing history and bookmarks are synced over iCloud when iCloud sync is enabled
- The Develop menu is enabled by default
- Receives regular updates through the Updates tab of the [Mac App Store](hmacappstore://showUpdatesPage)
- Bug reports made on [bugreport.apple.com](https://bugreport.apple.com/) should specify Safari Technology Preview

### JavaScript Improvements

- ECMAScript 6 support including lexical scoping, iterators, generators, arrow functions, default parameter values and many new built-in APIs
- Better standards compliant IndexedDB support with more stability
- Included the B3 JavaScript JIT compiler with low-latency, high-throughput that boosts performance
- Added the ability to use document.execCommand(‘copy’) and document.execCommand(‘cut’) in response to a user gesture to copy and cut text programmatically

### HTML Enhancements

- The latest implementation of the Shadow DOM specification
- Added support for Content Security Policy Level 2

### Web Inspector Changes

- Added memory summary and JavaScript allocations timelines
- Added a fast JavaScript sampling profiler
- Improved JavaScript profiling timeline view

### Behavior Changes

- Included many web compatibility fixes and bug fixes

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