Editing WebKit (section)

== Components ==

=== WebCore ===
WebCore is a layout, rendering, and [[Document Object Model]] (DOM) [[Library (computing)|library]] for HTML and [[Scalable Vector Graphics]] (SVG), developed by the WebKit project. Its full source code is licensed under the [[GNU Lesser General Public License]] (LGPL). The WebKit framework wraps WebCore and JavaScriptCore, providing an Objective-C [[application programming interface]] to the [[C++]]-based WebCore rendering engine and JavaScriptCore script engine, allowing it to be easily referenced by applications based on the [[Cocoa API]]; later versions also include a [[cross-platform]] C++ platform abstraction, and various ports provide more APIs.{{Citation needed|date=May 2021}}

WebKit passes the [[Acid2]] and [[Acid3]] tests, with pixel-perfect rendering and no timing or smoothness issues on reference hardware.<ref>{{cite web |url=https://webkit.org/blog/280/full-pass-of-acid-3/ |title=Full Pass Of Acid3 |access-date=September 29, 2008 |last=Stachowiak |first=Maciej |date=September 25, 2008 |work=Surfin' Safari – The WebKit Blog |url-status=live |archive-url=https://web.archive.org/web/20080929003302/http://webkit.org/blog/280/full-pass-of-acid-3/ |archive-date=September 29, 2008 |df=mdy-all }}</ref>

=== JavaScriptCore ===
JavaScriptCore is a framework that provides a [[JavaScript engine]] for WebKit implementations, and provides this type of scripting in other contexts within macOS.<ref name="annjavascript"/><ref name="webjavascript">{{cite web|url=https://webkit.org/projects/javascript/|title=The WebKit Open Source Project – JavaScript|url-status=live|archive-url=https://web.archive.org/web/20150814004755/http://www.webkit.org/projects/javascript/|archive-date=August 14, 2015|df=mdy-all}}</ref> JavaScriptCore is originally derived from [[KDE]]'s JavaScript engine ([[KJS (JavaScript engine)|KJS]]) [[Library (computing)|library]] (which is part of the KDE project) and the [[PCRE]] [[regular expression]] library. Since forking from KJS and PCRE, JavaScriptCore has been improved with many new features{{Such as|date=May 2025}} and greatly improved performance.<ref name="javascriptshowdown">{{cite web |title=The Great Browser JavaScript Showdown |url=http://www.codinghorror.com/blog/archives/001023.html |date=December 19, 2007 |url-status=live |archive-url=https://web.archive.org/web/20080906204651/http://www.codinghorror.com/blog/archives/001023.html |archive-date=September 6, 2008 |df=mdy-all }}</ref>

On June 2, 2008, the WebKit project announced they rewrote JavaScriptCore as "SquirrelFish", a [[bytecode]] [[Interpreter (computing)|interpreter]].<ref name="Announcing SquirrelFish"/><ref name="SquirrelFish project"/> The project evolved into SquirrelFish Extreme (abbreviated SFX, marketed as Nitro), announced on September 18, 2008 further speeding up JavaScript execution.<ref name="Introducing SquirrelFish Extreme" />

An optimizing [[Just-in-time compilation|just-in-time]] (JIT) compiler named ''FTL'' was announced on May 13, 2014.<ref name="ftljit">{{cite news|url=https://webkit.org/blog/3362/introducing-the-webkit-ftl-jit/|title=Introducing the WebKit FTL JIT|newspaper=Webkit |date=May 13, 2014|url-status=live|archive-url=https://web.archive.org/web/20170119202735/https://webkit.org/blog/3362/introducing-the-webkit-ftl-jit/|archive-date=January 19, 2017|df=mdy-all}}</ref> It uses [[LLVM]] to generate optimized machine code. "FTL" stands for "Fourth-Tier-LLVM", and unofficially for [[faster-than-light]], alluding to its speed.<ref>{{cite web|url=https://arstechnica.com/information-technology/2014/05/apple-integrates-llvm-compiler-to-boost-webkit-javascript-performance/|title=Apple integrates LLVM compiler to boost WebKit JavaScript performance|date=May 16, 2014|url-status=live|archive-url=https://web.archive.org/web/20170708093248/https://arstechnica.com/information-technology/2014/05/apple-integrates-llvm-compiler-to-boost-webkit-javascript-performance/|archive-date=July 8, 2017|df=mdy-all}}</ref> As of February 15, 2016, the backend of FTL JIT is replaced by "Bare Bones Backend" (or B3 for short).<ref>{{cite web|url=https://webkit.org/blog/5852/introducing-the-b3-jit-compiler/|title=Introducing the B3 JIT Compiler|date=February 15, 2016|url-status=live|archive-url=https://web.archive.org/web/20170503053344/https://webkit.org/blog/5852/introducing-the-b3-jit-compiler/|archive-date=May 3, 2017|df=mdy-all}}</ref>