Internet Explorer, using the Trident layout engine, almost fully supports HTML 4.01, CSS Level 1, XML 1.0 and DOM Level 1, with minor implementation gaps. It partially supports CSS Level 2 and DOM Level 2, with major implementation gaps and conformance issues. Full conformance to the CSS 2.1 specification is on the agenda for the final Internet Explorer 8 release. It has no support for XHTML, though it can render XHTML documents authored with HTML compatibility principles and served with a text/html MIME-type.

Internet Explorer uses DOCTYPE sniffing to choose between \"quirks mode\" (renders similarly to older versions of MSIE) and standards mode (renders closer to W3C\`s specifications) for HTML and CSS rendering on screen (for printing Internet Explorer always uses standards mode). It fully supports XSLT 1.0 or the December 1998 Working Draft of XSL, depending on the version of MSXML (a dynamic link library) available. It also provides its own dialect of ECMAScript called JScript.

Internet Explorer makes use of the accessibility framework provided in Windows. Internet Explorer is also a user interface for FTP, with operations similar to that of Windows Explorer (although this feature requires a shell window to be opened in recent versions of the browser, rather than natively within the browser). Visual Basic for Applications (VBA) is not supported, but available via extension (iMacros). Recent versions feature pop-up blocking and tabbed browsing. Tabbed browsing can also be added to older versions by installing Microsoft\`s MSN Search Toolbar or Yahoo\`s Yahoo Toolbar.

Internet Explorer uses a zone-based security framework that groups sites based on certain conditions, including whether it is an internet or intranet-based site as well as a user-editable whitelist. Security restrictions are applied on a per-zone basis; all the sites in a zone are subject to the restrictions.