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{{Short description|Software component that runs JavaScript}}
{{Use dmy dates|date=March 2024}}

The first [[software engine|engines]] for [[JavaScript]] were mere [[interpreter (computing)|interpreter]]s of the [[source code]], but all relevant modern engines use [[just-in-time compilation]] for improved performance.<ref>{{cite web |url=http://developer.telerik.com/featured/a-guide-to-javascript-engines-for-idiots/ |title=A Guide to JavaScript Engines for Idiots |last=Looper |first=Jen |publisher=[[Telerik]] Developer Network |date=2015-09-21 |archive-url=https://web.archive.org/web/20181208123231/http://developer.telerik.com/featured/a-guide-to-javascript-engines-for-idiots/ |access-date=2018-12-08 |archive-date=2018-12-08}}</ref> JavaScript engines are typically developed by [[web browser]] vendors, and every major browser has one. In a browser, the JavaScript engine runs in concert with the [[browser engine|rendering engine]] via the [[Document Object Model]] and [[Web IDL]] bindings.<ref>{{cite web |title=How Blink Works |url=https://docs.google.com/document/d/1aitSOucL0VHZa9Z2vbRJSyAIsAz24kX8LFByQ5xQnUg |publisher=Google |access-date=12 March 2024}}</ref> However, the use of JavaScript engines is not limited to browsers; for example, the [[V8 (JavaScript engine)|V8 engine]] is a core component of the [[Node.js]] [[runtime system]].<ref name="v8 doc">{{cite web |title=Documentation · V8 |url=https://v8.dev/docs |publisher=Google |access-date=3 March 2024}}</ref> They are also called [[ECMAScript]] engines, after the official name of the specification. With the advent of [[WebAssembly]], some engines can also execute this code in the same [[Sandbox (computer security)|sandbox]] as regular JavaScript code.<ref name="Wasm">{{cite web |last1=Nelaturu |first1=Keerthi |title=WebAssembly: What's the big deal? |url=https://medium.com/coinmonks/webassembly-whats-the-big-deal-662396ff1cd6 |website=medium.com |access-date=3 March 2024}}</ref><ref name="v8 doc" />

==History==
The first JavaScript engine was created by [[Brendan Eich]] in 1995 for the [[Netscape Navigator]] [[web browser]].<ref name="eich-history"/> It was a rudimentary [[Interpreter (computing)|interpreter]] for the nascent language Eich invented.<ref>{{Citation|last=Fin JS|title=Brendan Eich – CEO of Brave|date=June 17, 2016|url=https://www.youtube.com/watch?v=XOmhtfTrRxc |website=YouTube |access-date=February 7, 2018 }}</ref> (This evolved into the [[SpiderMonkey]] engine, still used by the [[Firefox]] browser.<ref name="eich-history">{{cite web |last1=Eich |first1=Brendan |title=New JavaScript Engine Module Owner |date=2011-06-21 |url=http://brendaneich.com/2011/06/new-javascript-engine-module-owner/}}</ref>) [[Google]] debuted its [[Google Chrome|Chrome]] browser in 2008, with the [[V8 (JavaScript engine)|V8]] JavaScript engine that was faster than its competition.<ref>{{cite web|url=https://www.pcgameshardware.com/aid,687738/Big-browser-comparison-test-Internet-Explorer-vs-Firefox-Opera-Safari-and-Chrome-Update-Firefox-35-Final/Practice/|title=Big browser comparison test: Internet Explorer vs. Firefox, Opera, Safari and Chrome|work=PC Games Hardware|date=3 July 2009|publisher=Computec Media AG|access-date=June 28, 2010|archive-date=May 2, 2012|archive-url=https://web.archive.org/web/20120502043027/http://www.pcgameshardware.com/aid,687738/Big-browser-comparison-test-Internet-Explorer-vs-Firefox-Opera-Safari-and-Chrome-Update-Firefox-35-Final/Practice/|url-status=live}}</ref><ref>{{cite web | url=https://lifehacker.com/lifehacker-speed-tests-safari-4-chrome-2-and-more-5286869 | title=Lifehacker Speed Tests: Safari 4, Chrome 2 | first=Kevin | last=Purdy | work=[[Lifehacker]] | date=June 11, 2009 | access-date=May 8, 2021 | archive-date=April 14, 2021 | archive-url=https://web.archive.org/web/20210414095403/https://lifehacker.com/lifehacker-speed-tests-safari-4-chrome-2-and-more-5286869 | url-status=live }}</ref> The key innovation was [[just-in-time compilation]] (JIT), which [[Mozilla]] had also been working on for SpiderMonkey.<ref>{{cite web|url=https://brendaneich.com/2008/08/tracemonkey-javascript-lightspeed/|title=TraceMonkey: JavaScript Lightspeed, Brendan Eich's Blog|access-date=July 22, 2020|archive-date=December 4, 2015|archive-url=https://web.archive.org/web/20151204091540/https://brendaneich.com/2008/08/tracemonkey-javascript-lightspeed/|url-status=live}}</ref> Because of V8's performance, the other browser vendors needed to overhaul their engines for JIT.<ref>{{cite magazine |title=Mozilla asks, 'Are we fast yet?' |url=https://www.wired.com/2010/09/mozilla-asks-are-we-fast-yet/ |magazine=Wired |access-date=January 18, 2019 |archive-date=June 22, 2018 |archive-url=https://web.archive.org/web/20180622213244/https://www.wired.com/2010/09/mozilla-asks-are-we-fast-yet/ |url-status=live }}</ref> [[Apple Inc.|Apple]] developed the [[WebKit#JavaScriptCore|Nitro]] engine for its [[Safari (web browser)|Safari]] browser, which had 30% better performance than its predecessor.<ref>[http://www.prnewswire.com/news-releases/apple-releases-safari-5-95817479.html Safari 5 Released]</ref> Mozilla then leveraged portions of Nitro to improve SpiderMonkey.<ref name="therace10">{{cite web |url=http://news.cnet.com/8301-30685_3-20000110-264.html |title=Opera 10.5 brings new JavaScript engine |last=Shankland |first=Stephen |date=2010-03-02 |work=CNET |publisher=CBS Interactive |access-date=2012-01-30 |archive-date=2013-10-03 |archive-url=https://web.archive.org/web/20131003051354/http://news.cnet.com/8301-30685_3-20000110-264.html |url-status=dead }}</ref> Since 2017, these engines have added support for [[WebAssembly]].<ref name="Wasm" />

== List ==
{| class="wikitable"
!Engine
!Description
|-
|[[V8 (JavaScript engine)|V8]]
|A JavaScript engine used in [[Google Chrome]] and other [[Chromium (web browser)|Chromium]]-based browsers (such as [[Microsoft Edge]]). Also used in [[Node.js]], [[Deno (software)|Deno]], and V8.NET.
|-
|[[SpiderMonkey]]
|A JavaScript engine in Mozilla [[Gecko (software)|Gecko]] applications, including [[Mozilla Firefox|Firefox]]. The engine currently includes the IonMonkey compiler and OdinMonkey optimization module, has previously included the TraceMonkey compiler (first JavaScript JIT) and JägerMonkey.
|-
|[[JavaScriptCore]]
|A JavaScript interpreter and JIT originally derived from [[KJS (software)|KJS]]. It is used in the [[WebKit]] project, applications such as [[Safari (web browser)|Safari]], and the [[Bun (software)|Bun]] runtime. Also known as Nitro, SquirrelFish, and SquirrelFish Extreme.<ref>{{Cite web |title=JavaScriptCore – WebKit |url=http://trac.webkit.org/wiki/JavaScriptCore}}</ref>
|-
|[[KJS (software)|KJS]]
|The engine used in [[Konqueror]], and one component of [[KHTML]], a predecessor to JavaScriptCore.
|-
|[[JScript]]
|The engine that is used in [[Internet Explorer]] for versions up to IE9, and one component of the [[MSHTML]] (Trident) [[browser engine]].
|-
|[[Chakra (JScript engine)|Chakra (JScript9)]]
|A [[JScript]] engine used in [[Internet Explorer]]. It was first previewed at [[MIX (Microsoft)#MIX 10|MIX 10]] as part of the Internet Explorer 9 Platform Preview.<ref>{{citation |title=Frequently Asked Questions |date=2010-03-13 |url=http://ie.microsoft.com/testdrive/info/FrequentlyAskedQuestions/Default.html |access-date=2010-03-18 |archive-url=https://web.archive.org/web/20100322193213/http://ie.microsoft.com/testdrive/info/FrequentlyAskedQuestions/Default.html |archive-date=2010-03-22 |url-status=dead |publisher=[[Microsoft]]}}</ref>
|-
|[[Chakra (JavaScript engine)|Chakra]]
|A [[JavaScript]] engine used in [[Microsoft Edge Legacy|Microsoft Edge [Legacy]]].<ref>{{cite web |title=Targeting Edge vs. Legacy Engines in JsRT APIs |url=https://msdn.microsoft.com/en-us/library/dn903710(v=vs.94).aspx |access-date=10 September 2015}}</ref>
|-
|[[Linear b (script engine)|Linear B]]
|The ECMAScript engine of the [[Opera (web browser)|Opera]] web browser versions 7.0 to 9.50, exclusive.
|-
|[[Futhark (script engine)|Futhark]]
|The ECMAScript engine of the [[Opera (web browser)|Opera]] web browser versions 9.50 to 10.10.
|-
|[[Carakan (script engine)|Carakan]]
|A JavaScript engine developed by [[Opera Software ASA]], included in the [[History of the Opera web browser#Version 10|10.50]] release of the [[Opera (web browser)|Opera]] web browser, until switching to [[V8 (JavaScript engine)|V8]] with Opera 15 (released in 2013).<ref>{{Cite web |title=Carakan |url=http://labs.opera.com/news/2009/02/05/ |url-status=dead |archive-url=https://web.archive.org/web/20090531095136/http://labs.opera.com/news/2009/02/05/ |archive-date=2009-05-31 |access-date=2009-07-09}}</ref><ref>{{Cite web |title=Opera Desktop Team's Blog &#124; Opera |url=http://my.opera.com/desktopteam/blog/ |archive-url=https://web.archive.org/web/20060303160759/http://my.opera.com/desktopteam/blog/ |archive-date=2006-03-03}}</ref><ref name="auto">{{Cite web |title=Dev.Opera — Blog |url=https://dev.opera.com/blog/ |website=dev.opera.com}}</ref>
|-
|Graal.js
|An ECMAScript compliant JavaScript engine for [[GraalVM]] which supports language interoperability that can also execute Node.js applications.
|-
|[[Rhino (JavaScript engine)|Rhino]]
|One of several JavaScript engines from [[Mozilla]], using the [[Java (software platform)|Java platform]].
|-
|[[Nashorn (JavaScript engine)|Nashorn]]
|A JavaScript engine used in [[Oracle Corporation|Oracle]] [[Java Development Kit]] (JDK) from Java versions 8-14.<ref>{{cite web |title=Oracle Nashorn: A Next-Generation JavaScript Engine for the JVM |url=http://www.oracle.com/technetwork/articles/java/jf14-nashorn-2126515.html}}</ref> Now available as a standalone library which can be used with Java 11 and higher.<ref>{{cite web |title=Using Nashorn with different Java versions |url=https://github.com/szegedi/nashorn/wiki/Using-Nashorn-with-different-Java-versions |access-date=23 January 2025 |website=[[GitHub]]}}</ref>
|-
|[[JScript .NET]]
|A [[.NET Framework]] [[JScript]] engine used in [[ASP.NET]] based on [[Common Language Runtime]] and [[COM Interop]]. Support was dropped with [[.NET Core]] and [[CoreCLR]] so its future looks questionable for [[ASP.NET Core]].
|-
|[[Tamarin (software)|Tamarin]]
|An [[ActionScript]] and ECMAScript engine used in [[Adobe Flash]].
|-
|[[GNU Guile]]
|features an ECMAScript interpreter as of version 1.9
|-
|iv
|ECMAScript Lexer / Parser / Interpreter / VM / method JIT written in C++.<ref>{{cite web|url=https://github.com/Constellation/iv|title=Constellation/iv|website=[[GitHub]]|access-date=2015-11-15}}</ref>
|-
|CL-JavaScript
|Can compile JavaScript to machine language on Common Lisp implementations that compile to machine language.<ref>{{cite web |title=CL-JavaScript |url=http://marijnhaverbeke.nl/cl-javascript/ |access-date=2018-09-14}}</ref>
|-
|BESEN
|A complete JIT-compiling implementation of ECMAScript Fifth Edition written in Object Pascal.<ref>{{Cite web |date=18 November 2021 |title=Support me |url=https://github.com/BeRo1985/besen |website=[[GitHub]]}}</ref>
|-
|Hermes
|developed by [[Facebook]] for [[React Native]] mobile apps<ref>{{cite web |title=Using Hermes |url=https://reactnative.dev/docs/hermes |access-date=9 April 2021 |publisher=Facebook}}</ref> Can also be used independent from React Native.
|-
|Continuum
|A [[self-interpreter]] that supports older drafts of the ECMAScript 2015 specification.<ref>{{cite web |title=ECMAScript 2015 Language Specification – ECMA-262 6th Edition |url=http://www.ecma-international.org/ecma-262/6.0/}}</ref> Uniquely, the engine is implemented in ECMAScript 3, which made it possible to run ES2015 in browsers as old as IE6.<ref>{{cite web |title=An ES6 Virtual Machine Built in JavaScript |url=https://benvie.github.com/continuum/ |url-status=dead |archive-url=https://web.archive.org/web/20121203041426/http://benvie.github.com/continuum/ |archive-date=2012-12-03 |access-date=2012-12-01}}</ref>
|-
|InScript
|An obsolete [[Proprietary software|proprietary]] library used for [[iCab]] 2 and 3.
|-
|Jint
|Javascript interpreter with integrated engine for .NET
|-
|Narcissus
|JavaScript implemented in JavaScript (a [[meta-circular evaluator]]), intended to run in another JavaScript engine, of theoretical and educational nature only.
|-
|JS-Interpreter
|A lightweight JavaScript interpreter implemented in JavaScript with step-by-step execution.
|-
|[[QtScript]]
|Originally developed by Trolltech, now owned by [[The Qt Company]]. It provides QObject integration with JavaScriptCore.
|-
|V4 (QJSEngine)
|Qt's newer ECMAScript engine, powering QML and QtQuick. ES6-compliant and under active development at [[The Qt Company]]. V4 is JIT compiled.<ref>{{Cite web |title=V4 - Qt Wiki |url=https://wiki.qt.io/V4 |access-date=2021-04-24 |website=wiki.qt.io}}</ref>
|-
|YAJI
|An ECMAScript engine based on the FESI implementation by Jean-Marc Lugrin in 1999, using the [[Java (software platform)|Java platform]], currently being developed to support the latest standards (ECMAScript spec. 262, v5.1).<ref>{{cite web |date=June 2011 |title=ECMAScript Language Specification ECMA-262 5.1 edition |url=http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-262.pdf |url-status=dead |archive-url=https://web.archive.org/web/20150412040502/http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-262.pdf |archive-date=2015-04-12 |access-date=2012-01-31 |publisher=Ecma International}}</ref><ref>{{cite web |title=YAJI: Yet Another JavaScript Interpreter |url=http://code.google.com/p/yaji-ecmascript-interpreter/ |access-date=2012-01-31 |work=Google Code}}</ref><ref>{{cite web |date=September 2003 |title=FESI |url=http://www.lugrin.ch/fesi |url-status=dead |archive-url=https://web.archive.org/web/20120906033028/http://www.lugrin.ch/fesi/ |archive-date=2012-09-06 |access-date=2012-08-06}}</ref>
|-
|Microvium
|JavaScript engine for microcontrollers, supporting a restricted subset of the ECMAScript specification, using less than 16{{nbsp}}kB of flash memory and 64{{nbsp}}B of RAM while idle.<ref>{{cite web |date=11 June 2022 |title=Microvium is very small |url=https://coder-mike.com/blog/2022/06/11/microvium-is-very-small/ |access-date=23 August 2022}}</ref>
|-
|Duktape
|A small footprint, easily embeddable Ecmascript E5/E5.1 engine.<ref>{{cite web |title=Duktape |url=http://www.duktape.org/ |access-date=2013-09-21}}</ref>
|-
|XS JavaScript Engine
|An ECMAScript 2020-compliant engine for microcontrollers with limited resources.<ref>{{Cite web |title=moddable/documentation/xs/XS Conformance.md at public |url=https://github.com/Moddable-OpenSource/moddable/blob/public/documentation/xs/XS%20Conformance.md#results |website=[[GitHub]]}}</ref><ref>{{cite web |title=Apps for IoT |url=https://www.moddable.com/faq.php#what-is-xs |url-status=dead |archive-url=https://web.archive.org/web/20181228063939/http://www.moddable.com/faq.php |archive-date=2018-12-28}}</ref> XS is maintained by Moddable as part of the Moddable SDK and was formerly part of the [[Kinoma|Kinoma Platform]].<ref>{{cite web |title=Xs7 @ Tc-39 |url=https://www.moddable.com/XS7-TC-39}}</ref>
|-
|Jsish
|An ES5.1 subset interpreter with builtin SQLite, JSON, WebSocket, and ZVFS support.<ref>{{cite web |title=Jsish |url=http://jsish.org/ |access-date=2014-04-30}}</ref>
|-
|[[Espruino]]
|A very small footprint interpreter specifically for [[Microcontroller|microcontrollers]]. Can run in less than 8 kB of RAM by executing from source (rather than [[bytecode]]).
|-
|MuJS
|A lightweight ECMAScript interpreter library, designed for embedding in other software to extend them with scripting capabilities. Originally developed for [[MuPDF]].<ref>{{cite web |title=MuJS |url=http://mujs.com/ |access-date=2014-09-22}}</ref>
|-
|mJS
|Restricted JavaScript engine. Used for Internet of Things (IoT).
|-
|Tiny-JS
|A minimal JavaScript interpreter written in C++.
|-
|JerryScript
|A lightweight JavaScript engine by Samsung for microcontrollers with less than 64 KB RAM.
|-
|njs
|A lightweight JavaScript interpreter optimized for web server scripting and fastest VM context creation; used in [[nginx]].<ref>{{cite web |date=26 October 2018 |title=NGINX JavaScript in Your Web Server Configuration |url=https://www.youtube.com/watch?v=Jc_L6UffFOs |url-status=live |archive-url=https://ghostarchive.org/varchive/youtube/20211213/Jc_L6UffFOs |archive-date=2021-12-13 |access-date=2018-10-30 |website=[[YouTube]]}}{{cbignore}}</ref>
|-
|quickjs
|A lightweight ECMAScript 6 interpreter by [[Fabrice Bellard]] and Charlie Gordon; it features a compiler to produce binary executable from .js.
|-
|engine262
|A JavaScript engine written in JavaScript for development and exploration. It is primarily used to validate the ECMAScript specification.
|-
|[[Boa (JavaScript engine)|Boa]]
|A JavaScript engine written in [[Rust (programming language)|Rust]].<ref>
{{Cite web |title=Let's build a JavaScript Engine |url=https://2019.jsconf.eu/jason-williams/lets-build-a-javascript-engine.html |access-date=2022-03-23 |website=2019.jsconf.eu |language=en}}</ref><ref>{{Cite web |title=GitHub - boa-dev/boa: Boa is an embeddable and experimental Javascript engine written in Rust. |url=https://github.com/boa-dev/boa |access-date=2022-04-08 |website=github.com |language=en}}</ref>
|-
|ScriptEase
|An old proprietary engine last updated in 2003. Only notable for its use in the [[James Webb Space Telescope]].<ref>{{Cite web |last=Clark |first=Mitchell |date=2022-08-18 |title=The James Webb Space Telescope runs JavaScript, apparently |url=https://www.theverge.com/2022/8/18/23206110/james-webb-space-telescope-javascript-jwst-instrument-control |access-date=2022-09-02 |website=The Verge |language=en}}</ref>
|-
|LibJS
|JavaScript engine of the [[SerenityOS]] and [[Ladybird (web browser)|Ladybird]] projects.<ref>{{Cite web |title=LibJS JavaScript engine |url=https://libjs.dev/ |access-date=2023-06-30 |website=libjs.dev}}</ref> Initially it was an AST interpreter, but has been upgraded to a bytecode-based one.<ref>{{Cite web |title=LibJS: Rip out the AST interpreter :^) · LadybirdBrowser/ladybird@2eaa528 |url=https://github.com/LadybirdBrowser/ladybird/commit/2eaa528a0ea606b2be9a1868ba711b1987409d70 |access-date=2024-07-10 |website=GitHub |language=en}}</ref>
|-
|Kiesel
|JavaScript engine by Linus Groh written in [[Zig (programming language)|Zig]].<ref>{{Cite web |title=Kiesel JavaScript Engine |url=https://kiesel.dev/ |access-date=2025-04-09 |website=kiesel.dev}}</ref><ref>{{Cite web |last=kiesel-js |title=kiesel |url=https://codeberg.org/kiesel-js/kiesel |access-date=2025-04-09 |website=Codeberg.org |language=en-US}}</ref><ref>{{Cite web |title=Linus Groh |url=https://linus.dev/ |access-date=2025-04-18 |website=linus.dev}}</ref>
|}

==References==
{{reflist|colwidth=30em}}

{{ECMAScript}}
{{JavaScript}}

{{DEFAULTSORT:JavaScript engine}}
[[Category:JavaScript engines| ]]

List of JavaScript engines - Revision history

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