Microsoft KB Archive/306790

= Description of Internet Explorer Support for Netscape-Style Plug-ins =

Article ID: 306790

Article Last Modified on 1/31/2007

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APPLIES TO


 * Microsoft Internet Explorer 5.5 Service Pack 2
 * Microsoft Internet Explorer 5.5 Service Pack 2
 * Microsoft Internet Explorer 5.5 Service Pack 2
 * Microsoft Internet Explorer 5.5 Service Pack 2
 * Microsoft Internet Explorer 5.5
 * Microsoft Internet Explorer 5.5 Service Pack 2
 * Microsoft Internet Explorer 6.0
 * Microsoft Internet Explorer 6.0
 * Microsoft Internet Explorer 6.0
 * Microsoft Internet Explorer 6.0
 * Microsoft Internet Explorer 6.0
 * Microsoft Internet Explorer 6.0
 * Microsoft Internet Explorer 6.0

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This article was previously published under Q306790



SUMMARY
This article describes Internet Explorer support for Netscape-style plug-ins.



MORE INFORMATION
Netscape-style plug-ins are supported in Internet Explorer 5.5 Service Pack 1 (SP1) and earlier, but are not supported in Internet Explorer 5.5 Service Pack 2 (SP2) and Internet Explorer 6.

Internet Explorer 5.5 SP2 and Internet Explorer 6 continue to support the Netscape EMBED tag, enabling content creators to provide components that are built on ActiveX technologies that achieve the same functionality as Netscape-style plug-ins. Customers who want to continue to use existing Netscape-style plug-ins in Internet Explorer 5.5 SP2 or Internet Explorer 6 cans use any of the following methods:
 * Contact the manufacturer of the Netscape-style plug-in to inquire whether the manufacturer has a version of the component available that is built on ActiveX technologies.
 * Rewrite existing Netscape-style plug-ins using ActiveX (or &quot;dual-author&quot; to support both Netscape-style plug-ins and ActiveX controls).
 * Write an ActiveX &quot;shim&quot; for the Netscape-style plug-in.

Background Information
A plug-in is a type of component framework that is used in Web development to display custom content within a browser. For many years, the Microsoft OLE technology (sometimes referred to as ActiveX) has enabled the creation of programmable elements for displaying video, sound, and other alternative data types. Microsoft designed this OLE technology so that it can be reused by other technologies. ActiveX technologies are used by standalone programs as well as by Web-based content and programs. In the online space, ActiveX can be used to achieve results similar to those obtained with Netscape style plug-ins.

The foundation of online content is an HTML document, which is generally viewed in a browser. In the HTML document, custom content can be incorporated either by using the W3C HTML 4.0 recommendation's OBJECT tag or by using the Netscape EMBED tag. Internet Explorer supports the use of ActiveX technology through either the OBJECT or the EMBED tag.

Netscape-Style Plug-ins in Windows
On the Windows platform, plug-ins are constructed as standard Win32 dynamic-link libraries (DLLs) that rely on a series of predefined entry points to expose functionality. They are given a window handle (HWND) by their container, which they then subclass to receive user interaction and operating system notifications through Windows messages.

ActiveX Controls
ActiveX controls are lightweight, reusable Component Object Model (COM) components. They are given a site (in the form of a COM interface pointer) by their container, and they use COM methods and interfaces to communicate with the container.

ActiveX controls are smaller, simplified versions of OLE controls (as defined by the OLE Controls 96 specification). ActiveX controls do not necessarily have an HWND.

OBJECT and EMBED Tags
The OBJECT tag is part of the W3C HTML 4.0 recommendation. The EMBED tag was introduced in Netscape Navigator. Internet Explorer uses ActiveX technologies to support both the OBJECT and EMBED tags; other browser and platform combinations use the Netscape plug-in technology to control components.

An advantage of the OBJECT tag over the EMBED tag is that it supports Internet Component Download, which is an operating system service for downloading and installing software from Web sites on the Internet and intranets. This service enables a software provider or Webmaster to &quot;package&quot; components and place them on Web servers for download. When users visit the Web site, Internet Component Download enables their browser to download and install the programs. This process can occur without the user having to restart the browser.

Recommendation
Whether you run Internet Explorer or a competitive browser, planning how to migrate to the latest release of a browser is critical. When you migrate to Internet Explorer 5.5 SP2 or Internet Explorer 6, determine in advance whether you need to convert existing Netscape-style plug-ins to ActiveX technology. You also need to identify and solve migration issues, such as incompatible plug-ins, before you attempt to migrate from your current browser to Internet Explorer 5.5 SP2 or Internet Explorer 6. You may need to redesign any Web pages that do not function properly.

Customers who want to upgrade to Internet Explorer 5 SP2 or Internet Explorer 6 and continue to provide functionality that is similar to existing Netscape-style plug-ins can use any of the following methods:
 * Contact the manufacturer of the Netscape-style plug-in to inquire whether the manufacturer has a version of the component available that is built on ActiveX technologies.
 * Rewrite existing Netscape-style plug-ins using ActiveX (or &quot;dual-author&quot; to support both Netscape-style plug-ins and ActiveX controls).
 * Write an ActiveX &quot;shim&quot; for the Netscape-style plug-in. The customer must deploy the shims to their customers. One shim is required per plug-in class ID.

The third-party products that are discussed in this article are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, regarding the performance or reliability of these products.

