Editing Internet Explorer (section)

==Extensibility==
Internet Explorer exposes a set of Component Object Model (COM) interfaces that allows [[Plug-in (computing)|add-ons]] to extend the functionality of the browser.<ref name="architecture" /> Extensibility is divided into two types: Browser extensibility and content extensibility. Browser extensibility involves adding [[context menu]] entries, toolbars, menu items or [[Browser Helper Objects]] (BHO). BHOs are used to extend the feature set of the browser, whereas the other extensibility options are used to expose that feature in the user interface. Content extensibility adds support for non-native content formats.<ref name="architecture" /> It allows Internet Explorer to handle new [[file format]]s and new [[network protocol|protocols]], e.g. [[WebM]] or SPDY.<ref name="architecture" /> In addition, web pages can integrate [[software widget|widgets]] known as ActiveX controls which run on Windows only but have vast potentials to extend the content capabilities; [[Adobe Flash Player]] and Microsoft Silverlight are examples.<ref name="architecture" /> Add-ons can be installed either locally, or directly by a web site.

Since malicious add-ons can compromise the security of a system, Internet Explorer implements several safeguards. Internet Explorer 6 with Service Pack 2 and later feature an Add-on Manager for enabling or disabling individual add-ons, complemented by a "No Add-Ons" mode. [[Security and safety features new to Windows Vista#Application isolation|Starting with Windows Vista]], Internet Explorer and its BHOs run with restricted [[Privilege (computing)|privileges]] and are isolated from the rest of the system. Internet Explorer 9 introduced a new component&nbsp;– Add-on Performance Advisor. Add-on Performance Advisor shows a notification when one or more of installed add-ons exceed a pre-set performance threshold. The notification appears in the Notification Bar when the user launches the browser. Windows 8 and Windows RT introduce a [[Metro-style app|Metro-style version]] of Internet Explorer that is entirely sandboxed and does not run add-ons at all.<ref name=":0">{{Cite web |last=McSherry |first=Tony |date=January 20, 2013 |title=A look at Internet Explorer 10 on Windows RT |url=http://www.techrepublic.com/blog/australian-technology/a-look-at-internet-explorer-10-on-windows-rt/ |archive-url=https://web.archive.org/web/20230204163922/https://www.techrepublic.com/article/a-look-at-internet-explorer-10-on-windows-rt |archive-date=4 February 2023 |website=[[TechRepublic]] |publisher=[[CBS Interactive]]}}</ref> In addition, Windows RT cannot download or install ActiveX controls at all; although existing ones bundled with Windows RT still run in the traditional version of Internet Explorer.<ref name=":0" />

Internet Explorer itself can be hosted by other applications via a set of COM interfaces. This can be used to embed the browser functionality inside a computer program or create [[Internet Explorer shell]]s.<ref name="architecture" />