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Netscape Plugin Application Programming Interface (NPAPI) is an application programming interface (API) that allows browser plugins to be developed. It was first developed for Netscape browsers, starting in 1995 with Netscape Navigator 2.0, but was subsequently adopted by other browsers. With the advent of HTML5, all major web browsers have removed support for 3rd party NPAPI plugins for security reasons. There are some smaller browsers such as Pale Moon and Waterfox Classic that retain support for NPAPI plugins.
In NPAPI architecture, a plugin declares content types (e.g. "audio/mp3") that it can handle. When the browser encounters a content type it cannot handle natively, it loads the appropriate plugin, sets aside space within the browser context for the plugin to render and then streams data to it. The plugin is responsible for rendering the data. The plugin runs in-place within the page, as opposed to older browsers that had to launch an external application to handle unknown content types. NPAPI requires each plugin to implement and expose approximately 15 functions for initializing, creating, deleting and positioning plugin content. NPAPI also supports scripting, printing, full-screen plugins, windowless plugins and content streaming.
NPAPI was frequently used for plugins which required intensive, low-level performance such as video players, including Adobe Flash Player and Microsoft Silverlight, as well as platforms for web applications such as the Java Runtime Environment.
LiveConnect was used in Netscape 4 to implement scriptability of NPAPI plugins.
The Open Java Interface-dependent implementation of LiveConnect was removed from the Mozilla source code tree in late June 2009 as part of the Mozilla 2 cleanup effort.It is no longer needed with the release of a redesigned Java Runtime Environment from Sun Microsystems. However the old implementation was restored for Gecko 1.9.2, as Apple had yet to port the newer JRE over to Mac OS X.
The disadvantage of LiveConnect is, that it is heavily tied to the version of Java embedded within the Netscape browser. This prevented the browser from using other Java runtimes, and added bloat to the browser download size, since it required Java to script plugins. Additionally, LiveConnect is tricky to program: The developer has to define a Java class for the plugin, run it through a specialized Java header compiler, and implement native methods. Handling strings, exceptions, and other Java objects from C++ is non-obvious. In addition, LiveConnect uses an earlier and now obsolete application programming interface (API) for invoking native C++ calls from Java, called JRI. The JRI technology has long since been supplanted by JNI.
Full privileges are only granted by default to chrome scripts, i.e. scripts that are part of the application or of an extension. For remote HTML/XHTML/XUL documents, most XPCOM objects are not accessible by the scripts as they have limited privileges due to security reasons. Even if they are accessible (e.g. the XMLHttpRequest object), the usual security restrictions can also be found (e.g. cannot open URLs of other domains).
Mozilla was already using XPCOM to define the interfaces to many objects implemented in C++. Each interface was defined by an IDL file, and run through an IDL compiler that produced header files and a language-neutral type library that was a binary representation of the interface. This binary described the interface, the methods, the parameters, the data structures and enumerations.
XPConnect has no Java dependency. However, the technology is based on XPCOM. Thus the plugin developer must be familiar with reference counting, interfaces and IDL to implement scripting. The dependency on XPCOM led to certain dynamic linking issues (e.g. the fragile base class problem) which had to be solved before the plugin would work correctly with different browsers. XPCOM has since been changed to supply a statically linked version to address such issues. This approach also requires an .xpt file to be installed next to the dynamic-link library (DLL); otherwise the plugin appears to work, but the scripting does not, causing confusion.
At the end of 2004, all major browser companies using NPAPI agreed on NPRuntimeas an extension to the original NPAPI to supply scripting, via an API that is similar in style to the old C-style NPAPI and is independent of other browser technologies like Java or XPCOM. It is only supported by Firefox ESR (Extended Support Release) and Safari.
Because of the age of the API, security issues, and adoption of alternative technologies such as HTML5, software vendors began to phase out NPAPI support in 2013.
The following list of web browsers support all NPAPI plugins:
Internet Explorer and browsers based on Internet Explorer use ActiveX controls, ActiveX documents and ActiveX scripting to offer in-page extensibility on par with NPAPI. Although commonly associated with Internet Explorer, ActiveX is integration technology that allows any computer program to integrate parts of other computer programs that support such integration.Internet Explorer, however, is discontinued and its replacement, Microsoft Edge, does not support ActiveX.
On 12 August 2009 a page on Google Codeintroduced a new project called Pepper, with the associated Pepper Plugin API (PPAPI); PPAPI is a derivative of NPAPI aimed to make plugins more portable and more secure. This extension is designed specifically to ease the implementation of out-of-process plugin execution.
PPAPI was initially only supported by Google Chrome and Chromium. Later, other Chromium-based browsers such as Opera and Vivaldi added PPAPI plugin support.
In February 2012 Adobe Systems announced that future Linux versions of Adobe Flash Player would be provided only via PPAPI. The previous release, Flash Player 11.2, with NPAPI support, would receive security updates for five years.In August 2016 Adobe announced that, contrary to their previous statement, it would again support the NPAPI Flash Player on Linux and keep releasing new versions of it.
In August 2020, Google announced that support for PPAPI would be removed from Google Chrome and Chromium in June 2022.
Adobe Flash is a multimedia software platform used for production of animations, rich web applications, desktop applications, mobile apps, mobile games, and embedded web browser video players. Flash displays text, vector graphics, and raster graphics to provide animations, video games, and applications. It allowed streaming of audio and video, and can capture mouse, keyboard, microphone, and camera input.
In computing, a plug-in is a software component that adds a specific feature to an existing computer program. When a program supports plug-ins, it enables customization.
Cross Platform Component Object Model (XPCOM) is a cross-platform component model from Mozilla. It is similar to Microsoft Component Object Model (COM) and Common Object Request Broker Architecture (CORBA). It features multiple language bindings and interface description language (IDL) descriptions; thus programmers can plug their custom functions into the framework and connect it with other components.
ActiveX is a deprecated software framework created by Microsoft that adapts its earlier Component Object Model (COM) and Object Linking and Embedding (OLE) technologies for content downloaded from a network, particularly from the World Wide Web. Microsoft introduced ActiveX in 1996. In principle, ActiveX is not dependent on Microsoft Windows operating systems, but in practice, most ActiveX controls only run on Windows. Most also require the client to be running on an x86-based computer because ActiveX controls contain compiled code.
The following tables compare general and technical information for a number of web browsers.
A rich web application is a web application that has many of the characteristics of desktop application software. The concept is closely related to a single-page application, and may allow the user interactive features such as drag and drop, background menu, WYSIWYG editing, etc. The concept was first introduced in 2002 by Macromedia to describe Macromedia Flash MX product. Throughout 2000-s, the term was generalized to describe web applications developed with other competing browser plugin technologies including Java applets, Microsoft Silverlight.
Mozilla Firefox has features that allow it to be distinguished from other web browsers, such as Chrome and Internet Explorer.
Add-on is the Mozilla term for software modules that can be added to the Firefox web browser and related applications. Mozilla hosts them on its official add-on website.
A browser extension is a small software module for customizing a web browser. Browsers typically allow a variety of extensions, including user interface modifications, ad blocking, and cookie management.
A local shared object (LSO), commonly called a Flash cookie, is a piece of data that websites that use Adobe Flash may store on a user's computer. Local shared objects have been used by all versions of Flash Player since version 6.
Microsoft Silverlight is a deprecated application framework designed for writing and running rich web applications, similar to Adobe's own runtime, Adobe Flash. A plugin for Silverlight is still available for a very small number of browsers. While early versions of Silverlight focused on streaming media, later versions supported multimedia, graphics, and animation, and gave support to developers for CLI languages and development tools. Silverlight was also one of the two application development platforms for Windows Phone, but web pages using Silverlight did not run on the Windows Phone or Windows Mobile versions of Internet Explorer, as there was no Silverlight plugin for Internet Explorer on those platforms.
Google Chrome is a cross-platform web browser developed by Google. It was first released in 2008 for Microsoft Windows built with free software components from Apple WebKit and Mozilla Firefox. It was later ported to Linux, macOS, iOS, and Android where it is the default browser built into the OS. The browser is also the main component of Chrome OS, where it serves as the platform for web applications.
Google Native Client (NaCl) is a sandboxing technology for running either a subset of Intel x86, ARM, or MIPS native code, or a portable executable, in a sandbox. It allows safely running native code from a web browser, independent of the user operating system, allowing web apps to run at near-native speeds, which aligns with Google's plans for Chrome OS. It may also be used for securing browser plugins, and parts of other applications or full applications such as ZeroVM.
The HTML5 specification introduced the video element for the purpose of playing videos, partially replacing the object element. HTML5 video is intended by its creators to become the new standard way to show video on the web, instead of the previous de facto standard of using the proprietary Adobe Flash plugin, though early adoption was hampered by lack of agreement as to which video coding formats and audio coding formats should be supported in web browsers. As of 2020, HTML5 video is the only widely supported video playback technology in modern browsers, with the Flash plugin being phased out.
HTML5 can be used as an alternative to some of the functionality of Adobe Flash. Both include features for playing audio and video within web pages. Flash is specifically built to integrate vector graphics and light games in a web page, features that HTML5 also supports.
Pale Moon is an open-source web browser with an emphasis on customizability; its motto is "Your browser, Your way". There are official releases for Microsoft Windows and Linux, as well as contributed builds for various platforms.