[10][11] On January 7, 2003, at Macworld San Francisco, Apple CEO Steve Jobs announced Safari that was based on[12] WebKit, the company's internal fork of the KHTML browser engine.

These major changes were initially unavailable for end-users unless they privately installed and compiled the WebKit source code or ran one of the nightly automated builds available at OpenDarwin.

[19] In June 2005 in response to KHTML criticisms over the lack of access to change logs, Apple moved the development source code and bug tracking of WebCore and JavaScriptCore to OpenDarwin.

[36] Safari 3.2, released on November 13, 2008, introduced anti-phishing features using Google Safe Browsing and Extended Validation Certificate support.

[43] Safari 4 relied on Cover Flow to run the History and Bookmarks, and it featured Speculative Loading that automatically pre-loaded document information that is required to visit a particular website.

The update also commissioned many developer tool improvements including Web Inspectors, CSS element viewings, JavaScript debuggers and profilers, offline tables, database management, SQL support and resource graphs.

It added supports for full-screen video, closed caption, geolocation, EventSource, and a now obsolete early variant of the WebSocket protocol.

[63] The sixth major version of Safari, it added options to allow pages to be shared with other users via email, Messages, Twitter, and Facebook, as well as making some minor performance improvements.

It included the JavaScript API WebGL, stronger privacy management, improved iCloud integration, and a redesigned interface.

[68] It was also faster and more efficient, with additional developer features including JavaScript Promises, CSS Shapes & Composting mark up, IndexedDB, Encrypted Media Extensions, and SPDY protocol.

Software improvements included Autofill quality from the Contrast card and Web Inspector Timelines Tab, in-line sub-headlines, bylines, and publish dates.

Safari 16 also includes shared tab groups, vertical tab support, website settings synchronization between devices connected to a same iCloud account, the ability to add backgrounds for a start page,[99] new languages for built-in translation, built-in image translation, and new options to edit strong passwords.

Other new features include a redesigned unified menu which is now on all versions of the browser, previously it was exclusive to iOS and iPadOS along with the compact mode on macOS, and faster loading times.

[150] In September 2017, Apple announced that it would use artificial intelligence (AI) to reduce the ability of advertisers to track Safari users as they browse the web.

[152] Apple used a remotely updated plug-in blacklist to prevent potentially dangerous or vulnerable plugins from running on Safari.

Internally, the update limited the number of blocking rules[155] which could be applied by third-party extensions, preventing the full implementation of community-developed blocklists.

In response, several developers of popular ad and tracking blockers announced their products were being discontinued,[156] as they were now incompatible with Safari's newly limited content blocking features.

Users can also easily lift the subject of an image from Safari, remove its background, and paste it into other apps like Messages and Notes.

[164] The Quick Note feature lets users capture thoughts or jot down ideas while browsing, directly within Safari.

[166] A new feature powered by machine learning, Highlights automatically surfaces contextual information like summaries, quick links, and related content based on web activity.

[167] Distraction Control lets users hide specific elements on a webpage that might be visually disruptive, allowing for a cleaner browsing experience and improved focus on the content.

Like KHTML and KJS, WebCore and JavaScriptCore are free software and released under the terms of the GNU Lesser General Public License.

Apple improved multitouch compatibility for desktop websites through a number of tweaks to the WebKit engine, for example with heuristics to determine whether to translate a tap into a hover or a click.

[186] A Safari version for visionOS released with the launch of the Apple Vision Pro headset in 2024, with features specific to the platform such as moving browser windows around in virtual space.

[206] Software security firm Sophos detailed how Snow Leopard and Windows users were not supported by the Safari 6 release at the time,[207] while there were over 121 vulnerabilities left unpatched on those platforms.

[210] While no official word has been released by Apple, the indication is that these are the final versions available for these operating systems, and both retain significant security issues.

[215] Apple's stated motivation for this browser engine restriction was to increase security, an argument disputed by the UK's Competition and Markets Authority.

[216] The European Union's Digital Markets Act regulation, passed in 2022, requires Apple to allow alternative browser engines.

Both Apple and Google have argued that disclosing the specific terms of their search default agreement would harm their competitive positions.

This revelation has raised concerns about the dominance of Google in the search engine market and the potential anticompetitive effects of its agreements with Apple.