Users of Microsoft Windows HTTP Services (WinHTTP) should use the latest version of the technology, version 5.1.

Version 5.1

WinHTTP 5.1 offers improvements over version 5.0; for more information about new features, see What's New in WinHTTP 5.1.

With version 5.1, WinHTTP is now an operating-system component of the following operating systems:

• Windows 2000, Service Pack 3 and later (except Datacenter Server)
• Windows XP with Service Pack 1 (SP1) and later
• Windows Server 2003 with Service Pack 1 (SP1) and later

For Windows Server 2003 with SP1, WinHTTP is a system side-by-side assembly. For more information, see Side-by-side Assemblies.

Redistribution of WinHTTP 5.1 outside of these operating systems is not supported; for example, WinHTTP 5.1 is not supported on Windows NT 4.0.

Version 5.0

The WinHTTP 5.0 redistributable, "winhttp5.dll", runs on Windows 2000 or later, or Windows NT 4.0 with Microsoft Internet Explorer 5.01 or later.

Important  With the release of WinHTTP Version 5.1, the WinHTTP 5.0 download is no longer available. As of October 1, 2004, Microsoft has removed the WinHTTP 5.0 SDK download from MSDN and has terminated product support for version 5.0.

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Build date: 7/9/2009