InternetSetOptionA function (wininet.h)

Sets an Internet option.


BOOL InternetSetOptionA(
  [in] HINTERNET hInternet,
  [in] DWORD     dwOption,
  [in] LPVOID    lpBuffer,
  [in] DWORD     dwBufferLength


[in] hInternet

Handle on which to set information.

[in] dwOption

Internet option to be set. This can be one of the Option Flags values.

[in] lpBuffer

Pointer to a buffer that contains the option setting.

[in] dwBufferLength

Size of the lpBuffer buffer. If lpBuffer contains a string, the size is in TCHARs. If lpBuffer contains anything other than a string, the size is in bytes.

Return value

Returns TRUE if successful, or FALSE otherwise. To get a specific error message, call GetLastError.


GetLastError will return the error ERROR_INVALID_PARAMETER if an option flag that cannot be set is specified.

For more information, see Setting and Retrieving Internet Options.

Like all other aspects of the WinINet API, this function cannot be safely called from within DllMain or the constructors and destructors of global objects.

Note  WinINet does not support server implementations. In addition, it should not be used from a service. For server implementations or services use Microsoft Windows HTTP Services (WinHTTP).


The wininet.h header defines InternetSetOption as an alias which automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.


Requirement Value
Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Target Platform Windows
Header wininet.h
Library Wininet.lib
DLL Wininet.dll

See also

Common Functions






WinINet Functions