Option flags
The following option flags are supported by WinHttpQueryOption and WinHttpSetOption.
WINHTTP_OPTION_ASSURED_NON_BLOCKING_CALLBACKS
The default is FALSE. If set to TRUE, WinHTTP doesn't guarantee progress if status callbacks are blocked by the client application.
The client application must take special care to perform minimal operations within the callback without blocking, returning as quickly as possible, and in particular must not wait for any subsequent WinHTTP calls. If it doesn't follow these guidelines, there is likely to be a negative performance impact or a potential application hang. If used in the prescribed manner, this option may improve performance.
WINHTTP_OPTION_AUTOLOGON_POLICY
Sets an unsigned long integer value that specifies the Automatic Logon Policy with one of the following values.
| Term | Description |
|---|---|
| WINHTTP_AUTOLOGON_SECURITY_LEVEL_HIGH | Default credentials are not used. Note that this flag takes effect only if you specify the server by the actual machine name. It will not take effect, if you specify the server by "localhost" or IP address. |
| WINHTTP_AUTOLOGON_SECURITY_LEVEL_LOW | An authenticated log on using the default credentials is performed for all requests. |
| WINHTTP_AUTOLOGON_SECURITY_LEVEL_MEDIUM | An authenticated log on using the default credentials is performed only for requests on the local Intranet. |
WINHTTP_OPTION_BACKGROUND_CONNECTIONS
When you set this option on a session handle, you must pass the number of connections you wish to open. Then, upon first sending a request, rather than opening only a single connection, WinHttp opens a number of connections in parallel. This can improve the performance of subsequent requests to the same destination, which won't have the overhead of connection establishment.
WINHTTP_OPTION_CALLBACK
Retrieves the pointer to the callback function set with WinHttpSetStatusCallback.
WINHTTP_OPTION_CLIENT_CERT_CONTEXT
Sets the client certificate context. If an application receives ERROR_WINHTTP_CLIENT_AUTH_CERT_NEEDED, it must call WinHttpSetOption to supply a certificate before retrying the request. As a part of processing this option, WinHttp calls CertDuplicateCertificateContext on the caller-provided certificate context so that the certificate context can be independently released by the caller.
Note
The application should not attempt to close the certificate store with the CERT_CLOSE_STORE_FORCE_FLAG flag in the call to CertCloseStore on the certificate store from which the certificate context was retrieved. An access violation may occur.
When the server requests a client certificate, WinHttpSendRequest, or WinHttpReceiveResponse returns an ERROR_WINHTTP_CLIENT_AUTH_CERT_NEEDED error. If the server requests the certificate but doesn't require it, the application can specify this option to indicate that it doesn't have a certificate. The server can choose another authentication scheme or allow anonymous access to the server. The application provides the WINHTTP_NO_CLIENT_CERT_CONTEXT macro in the lpBuffer parameter of WinHttpSetOption as shown in the following code example.
BOOL fRet = WinHttpSetOption(hRequest,
WINHTTP_OPTION_CLIENT_CERT_CONTEXT,
WINHTTP_NO_CLIENT_CERT_CONTEXT,
0);
If the server requires a client certificate, it may send a 403 HTTP status code in response. For more information, see the WINHTTP_OPTION_CLIENT_CERT_ISSUER_LIST option.
WINHTTP_OPTION_CLIENT_CERT_ISSUER_LIST
Retrieves a SecPkgContext_IssuerListInfoEx structure when the error from WinHttpSendRequest or WinHttpReceiveResponse is ERROR_WINHTTP_CLIENT_AUTH_CERT_NEEDED. The issuer list in the structure contains a list of acceptable Certificate Authorities (CA) from the server. The client application can filter the CA list to retrieve the client certificate for SSL authentication.
Alternately, if the server requests the client certificate, but doesn't require it, the application can call WinHttpSetOption with the WINHTTP_OPTION_CLIENT_CERT_CONTEXT option. For more information, see the WINHTTP_OPTION_CLIENT_CERT_CONTEXT option.
WINHTTP_OPTION_CODEPAGE
Sets the code page that is used to process the URL (that is, query string). The default is UTF8.
WINHTTP_OPTION_CONFIGURE_PASSPORT_AUTH
Sets an unsigned long integer value that specifies whether Passport Authentication in WinHTTP authentication is enabled. The value can be one of the following:
| Term | Description |
|---|---|
| WINHTTP_DISABLE_PASSPORT_AUTH | Microsoft Passport authentication is disabled. This is the default. |
| WINHTTP_DISABLE_PASSPORT_KEYRING | The Passport keyring is disabled. This is the default. |
| WINHTTP_ENABLE_PASSPORT_AUTH | Passport authentication is enabled. |
| WINHTTP_ENABLE_PASSPORT_KEYRING | The Passport keyring is enabled. |
WINHTTP_OPTION_CONNECT_RETRIES
Sets or retrieves an unsigned long integer value that contains the number of timesWinHTTP attempts to connect to a host. Microsoft Windows HTTP Services (WinHTTP) only attempts once per Internet Protocol (IP) address. For example, if you attempt to connect to a multihomed host that has 10 IP addresses and WINHTTP_OPTION_CONNECT_RETRIES is set to 7, then WinHTTP only attempts to connect to the first seven IP address. Given the same set of 10 IP addresses, if WINHTTP_OPTION_CONNECT_RETRIES is set to 20, WinHTTP attempts each of the 10 only once. If a connection attempt still fails after the specified number of attempts, or if the connect timeout expired before then, the request is canceled. The default value for WINHTTP_OPTION_CONNECT_RETRIES is five attempts.
WINHTTP_OPTION_CONNECT_TIMEOUT
Sets or retrieves an unsigned long integer value that contains the time-out value, in milliseconds. Setting this option to infinite (0xFFFFFFFF) will disable this timer.
If a TCP connection request takes longer than this time-out value, the request is canceled. The default timeout is 60 seconds. When you are attempting to connect to multiple IP addresses for a single host (a multihomed host), the timeout limit is for each individual connection.
WINHTTP_OPTION_CONNECTION_INFO
Retrieves the source and destination IP address, and port of the request that generated the response when WinHttpReceiveResponse returns. The application calls WinHttpQueryOption with the WINHTTP_OPTION_CONNECTION_INFO option, and provides the WINHTTP_CONNECTION_INFO structure in the lpBuffer parameter. For more information, see WINHTTP_CONNECTION_INFO.
Applies to: Windows XP with SP2 and later; Windows 2003 with SP1 and later.
WINHTTP_OPTION_CONNECTION_GUID
Mark the connection associated with the WinHTTP request handle with a GUID. This allows custom control over which requests use which groups of connections with the WINHTTP_OPTION_MATCH_CONNECTION_GUID option.
WINHTTP_OPTION_CONNECTION_STATS_V0
Retreives the TCP_INFO_v0 struct for the underlying connection used by the request. The returned struct may contain statistics from prior requests sent over the same connection.
Note
This option has been superseded by WINHTTP_OPTION_CONNECTION_STATS_V1.
WINHTTP_OPTION_CONNECTION_STATS_V1
Retreives the TCP_INFO_v1 struct for the underlying connection used by the request. The returned struct may contain statistics from prior requests sent over the same connection.
WINHTTP_OPTION_CONTEXT_VALUE
Sets or retrieves a DWORD_PTR that contains a pointer to the context value associated with this HINTERNET handle. The value stored in the buffer is used and the WINHTTP_OPTION_CONTEXT_VALUE option flag is assigned a new value.
WINHTTP_OPTION_DECOMPRESSION
Sets a DWORD of flags which determine whether WinHTTP will automatically decompress response bodies with compressed Content-Encodings. WinHTTP will also set an appropriate Accept-Encoding header, overriding any supplied by the caller. Supported values are:
| Term | Description |
|---|---|
| WINHTTP_DECOMPRESSION_FLAG_GZIP | Decompress Content-Encoding: gzip responses. |
| WINHTTP_DECOMPRESSION_FLAG_DEFLATE | Decompress Content-Encoding: deflate responses. |
| WINHTTP_DECOMPRESSION_FLAG_ALL | Decompress responses with any supported Content-Encoding. |
By default, WinHTTP will deliver compressed responses to the caller unmodified.
WINHTTP_OPTION_DISABLE_CERT_CHAIN_BUILDING
Setting this option on a WinHttp session handle allows you to enable/disable whether the server certificate chain is built.
WINHTTP_OPTION_DISABLE_FEATURE
Sets an unsigned long integer value that specifies which features are disabled with one or more of the following flags. Be aware that this feature should only be passed to WinHttpSetOption on request handles after the request handle is created with WinHttpOpenRequest, and before the request is sent with WinHttpSendRequest.
| Term | Description |
|---|---|
| WINHTTP_DISABLE_AUTHENTICATION | Automatic authentication is disabled. |
| WINHTTP_DISABLE_COOKIES | Automatic addition of cookie headers to requests is disabled. Also, returned cookies are not automatically added to the cookie database. Disabling cookies can result in poor performance for Passport authentication. |
| WINHTTP_DISABLE_KEEP_ALIVE | Disables keep-alive semantics for the connection. Keep-alive semantics are required for MSN, NTLM, and other types of authentication. |
| WINHTTP_DISABLE_REDIRECTS | Automatic redirection is disabled when sending requests with WinHttpSendRequest. If automatic redirection is disabled, an application must register a callback function in order for Passport authentication to succeed. |
WINHTTP_OPTION_DISABLE_GLOBAL_POOLING
Disables global, cross-session pooling. This is recommended practice because global, cross-session pooling is legacy behavior that's supported by default for compatibility reasons. This is impacted by later setting max connections manually.
WINHTTP_OPTION_DISABLE_PROXY_AUTH_SCHEMES
Disables one or more of the following proxy authentication practices on the WinHTTP session by providing the OR of all applicable choices. These are all schemes, except for WINHTTP_PROXY_DISABLE_AUTH_LOCAL_SERVICE, which forces the use of the local machine account when sending requests to a loopback or local address. That prevents leaking system credentials to local HTTP proxies.
| Term | Description |
|---|---|
| WINHTTP_PROXY_DISABLE_SCHEME_BASIC | Disables the Basic authentication scheme. |
| WINHTTP_PROXY_DISABLE_SCHEME_DIGEST | Disables the Digest authentication scheme. |
| WINHTTP_PROXY_DISABLE_SCHEME_NTLM | Disables the NTLM authentication scheme. |
| WINHTTP_PROXY_DISABLE_SCHEME_KERBEROS | Disables the Kerberos authentication scheme. |
| WINHTTP_PROXY_DISABLE_SCHEME_NEGOTIATE | Disables the Negotiate authentication scheme. |
| WINHTTP_PROXY_DISABLE_AUTH_LOCAL_SERVICE | Forces the use of the local machine account when sending requests to a loopback or local address. |
WINHTTP_OPTION_DISABLE_SECURE_PROTOCOL_FALLBACK
Prevents WinHTTP from retrying a connection with a lower version of the security protocol when the initial protocol negotiation fails.
WINHTTP_OPTION_DISABLE_STREAM_QUEUE
Allows new requests to open an additional HTTP/2 connection when the maximum concurrent stream limit is reached, rather than waiting for the next available stream on an existing connection.
WINHTTP_OPTION_ENABLE_FEATURE
Sets an unsigned long integer value that specifies the features currently enabled. Can be one of the following values.
| Term | Description |
|---|---|
| WINHTTP_ENABLE_SSL_REVERT_IMPERSONATION | If enabled, WinHTTP temporarily reverts client impersonation for the duration of SSL certificate authentication operations. This value can be set only on the session handle. |
| WINHTTP_ENABLE_SSL_REVOCATION | If enabled, WinHTTP allows SSL revocation. This value can be set only on the request handle. |
WINHTTP_OPTION_ENABLE_HTTP_PROTOCOL
Sets a DWORD bitmask of acceptable advanced HTTP versions. Possible values are:
| Term | Description |
|---|---|
| WINHTTP_PROTOCOL_FLAG_HTTP2 (0x1) | Enables HTTP/2 for the request. |
| WINHTTP_PROTOCOL_FLAG_HTTP3 (0x2) | Enables HTTP/3 for the request. |
| None (0x0) | Restricts the request to HTTP/1.1 and prior. |
Legacy versions of HTTP (1.1 and prior) can't be disabled using this option. The default is 0x0.
WINHTTP_OPTION_ENABLE_HTTP2_PLUS_CLIENT_CERT
This option can be set on a WinHttp session handle to allow WinHttp to use the caller-provided client certificate context when HTTP/2 is being used.
WINHTTP_OPTION_ENABLETRACING
Sets a BOOL value that specifies whether tracing is currently enabled. This option can be set only on a NULL HINTERNET handle. Also see Collect WinHTTP traces.
WINHTTP_OPTION_ENCODE_EXTRA
Enables URL percent encoding for path and query string.
Alternatively, you can percent encode before calling WinHttp.
WINHTTP_OPTION_EXPIRE_CONNECTION
This option can only be set on a request handle which is still active (sending or receiving). Setting this option will tell WinHttp to stop serving requests on the connection associated with the request handle passed in. The connection will be closed after the request handle this option is called with is completed. This option doesn't take any parameters.
WINHTTP_OPTION_EXTENDED_ERROR
Retrieves an unsigned long integer value that contains a Microsoft Windows Sockets error code that was mapped to the ERROR_WINHTTP_* error messages last returned in this thread context. You can pass NULL as the handle value.
WINHTTP_OPTION_FEATURE_SUPPORTED
Check to see whether a provided option flag is supported by this version of WinHTTP.
WINHTTP_OPTION_FIRST_AVAILABLE_CONNECTION
By default, when WinHttp sends a request, if there are no available connections to serve the request, WinHttp will attempt to establish a new connection, and the request will be bound to this new connection. When you set this option, such a request will instead be served on the first connection that becomes available, and not necessarily the one being established.
WINHTTP_OPTION_GLOBAL_PROXY_CREDS
Takes a pointer to a WINHTTP_CREDS_EX structure with the hInternet function parameter set to NULL. This option requires registry key HKLM\Software\Microsoft\Windows\CurrentVersion\Internet Settings!ShareCredsWithWinHttp. If this registry key is not set WinHTTP will return error ERROR_WINHTTP_INVALID_OPTION. This registry key is not present by default. When it is set, WinINet will send credentials down to WinHTTP. Whenever WinHttp gets an authentication challenge and if there are no credentials set on the current handle, it will use the credentials provided by WinINet. In order to share server credentials in addition to proxy credentials, users needs to set WINHTTP_OPTION_USE_GLOBAL_SERVER_CREDENTIALS .
WINHTTP_OPTION_GLOBAL_SERVER_CREDS
Takes a pointer to a WINHTTP_CREDS_EX structure with the hInternet function parameter set to NULL. This option requires registry key HKLM\Software\Microsoft\Windows\CurrentVersion\Internet Settings!ShareCredsWithWinHttp. If this registry key is not set WinHTTP will return error ERROR_WINHTTP_INVALID_OPTION. This registry key is not present by default. When it is set, WinINet will send credentials down to WinHTTP. Whenever WinHttp gets an authentication challenge and if there are no credentials set on the current handle, it will use the credentials provided by WinINet. In order to share server credentials in addition to proxy credentials, users needs to set WINHTTP_OPTION_USE_GLOBAL_SERVER_CREDENTIALS .
WINHTTP_OPTION_HANDLE_TYPE
Retrieves an unsigned long integer value that contains the type of the HINTERNET handle passed in. The return value can be one of the following:
| Term | Description |
|---|---|
| WINHTTP_HANDLE_TYPE_CONNECT | The handle is a connection handle. |
| WINHTTP_HANDLE_TYPE_REQUEST | The handle is a request handle. |
| WINHTTP_HANDLE_TYPE_SESSION | The handle is a session handle. |
WINHTTP_OPTION_HTTP_PROTOCOL_REQUIRED
Prevents protocol versions other than those enabled by WINHTTP_OPTION_ENABLE_HTTP_PROTOCOL from being used for the request.
WINHTTP_OPTION_HTTP_PROTOCOL_USED
Gets a DWORD indicating which advanced HTTP version was used on a given request. For a list of possible values, see WINHTTP_OPTION_ENABLE_HTTP_PROTOCOL.
WINHTTP_OPTION_HTTP_VERSION
Sets or retrieves an HTTP_VERSION_INFO structure that contains the HTTP version being supported. This is a process-wide option; use NULL for the handle.
WINHTTP_OPTION_HTTP2_KEEPALIVE
This option can be set on a session handle to have WinHttp use HTTP/2 PING frames as a keepalive mechanism. Callers specify a timeout in milliseconds, and after there is no activity on a connection for that timeout period, WinHttp will begin to send HTTP/2 PING frames. Callers cannot set a timeout value less than 5000 milliseconds.
WINHTTP_OPTION_HTTP2_PLUS_TRANSFER_ENCODING
This option can be set on a WinHttp request handle to control how WinHttp behaves when an HTTP/2 response contains a "Transfer-Encoding" header. In such a case, WinHttp will return an error if this option is set to FALSE.
WINHTTP_OPTION_HTTP2_RECEIVE_WINDOW
Set the initial HTTP/2 stream receive window size and the threshold for sending window updates using the WINHTTP_HTTP2_RECEIVE_WINDOW struct.
WINHTTP_OPTION_HTTP3_HANDSHAKE_TIMEOUT
Uses the buffer to set the HTTP/3 handshake timeout in milliseconds as a PDWORD.
WINHTTP_OPTION_HTTP3_INITIAL_RTT
Configures the initial RTT in milliseconds used by msquic.
WINHTTP_OPTION_HTTP3_KEEPALIVE
Enables keep-alive semantics for the connection. Uses the buffer to set the keep-alive timeout in milliseconds as a PDWORD.
WINHTTP_OPTION_HTTP3_STREAM_ERROR_CODE
Retrieves the server-provided error on the HTTP/3 stream used to send the request.
WINHTTP_OPTION_IGNORE_CERT_REVOCATION_OFFLINE
Allows secure connections to use security certificates for which the certificate revocation list could not be downloaded.
WINHTTP_OPTION_IPV6_FAST_FALLBACK
Enables IPv6 fast fallback (Happier Eyeballs) for the connection. This behavior is similar to the Happy Eyeballs behavior described in RFC 6555 for improving connection times on networks where IPv6 is unreliable.
- If both IPv6 and IPv4 addresses are resolved for a given host, WinHttp will begin by connecting to the first resolved IPv6 address with a short (300ms) timeout.
- Should that connection fail, WinHttp will attempt to connect to the first resolved IPv4 address with the standard timeout.
- Should the second connection fail, WinHttp will retry the first resolved IPv6 address with the standard timeout.
- Should the third connection fail, WinHttp will revert to the default behavior for any remaining addresses, attempting a connection to each one with the standard timeout until a connection is made or no addresses remain.
WINHTTP_OPTION_IS_PROXY_CONNECT_RESPONSE
Gets whether or not a Proxy Return Connect Response can be retrieved.
WINHTTP_OPTION_MATCH_CONNECTION_GUID
Takes a WINHTTP_MATCH_CONNECTION_GUID struct to tell WinHTTP to serve the request on a matching connection. If WINHTTP_MATCH_CONNECTION_GUID_FLAG_REQUIRED is set, then only connections with a matching GUID can be used. Otherwise, connections with matching GUIDs and connections that are not marked with any GUID can be used.
WINHTTP_OPTION_MAX_CONNS_PER_1_0_SERVER
Sets or retrieves an unsigned long integer value that contains the maximum number of connections allowed per HTTP/1.0 server. The default value is INFINITE.
Applies to: Windows Vista with SP1 and later; Windows Server 2008 and later.
WINHTTP_OPTION_MAX_CONNS_PER_SERVER
Sets or retrieves an unsigned long integer value that contains the maximum number of connections allowed per server. The default value is INFINITE.
When this option is set to zero, WinHTTP sets the limit on the number of connections to 2.
WINHTTP_OPTION_MAX_HTTP_AUTOMATIC_REDIRECTS
Sets the maximum number of redirects that WinHTTP follows; the default is 10. This limit prevents unauthorized sites from making the WinHTTP client pause following a large number of redirects.
Applies to: Windows XP with SP1 and later; Windows 2000 with SP3 and later.
WINHTTP_OPTION_MAX_HTTP_STATUS_CONTINUE
The maximum number of Informational 100-199 status code responses ignored before returning the final status code to the WinHTTP client. Informational 100-199 status codes can be sent by the server before the final status code, and are described in the specification for HTTP/1.1 (for more information, see RFC 2616). The default is 10.
Applies to: Windows XP with SP1 and later; Windows 2000 with SP3 and later.
WINHTTP_OPTION_MAX_RESPONSE_DRAIN_SIZE
A bound on the amount of data drained from responses in order to reuse a connection, specified in bytes. The default is 1MB.
Applies to: Windows XP with SP1 and later; Windows 2000 with SP3 and later.
WINHTTP_OPTION_MAX_RESPONSE_HEADER_SIZE
A bound set on the maximum size of the header portion of the server response, specified in bytes. This bound protects the client from an unauthorized server attempting to stall the client by sending a response with an infinite amount of header data. The default value is 64KB.
Applies to: Windows XP with SP1 and later; Windows 2000 with SP3 and later.
WINHTTP_OPTION_PARENT_HANDLE
Retrieves the parent handle to this handle.
WINHTTP_OPTION_PASSPORT_COBRANDING_TEXT
Retrieves a string that contains the cobranding text provided by the Passport logon server. This option should be retrieved immediately after the logon server responds with a 401 status code. An application should pass in a buffer size, in bytes, that is big enough to hold the returned string.
WINHTTP_OPTION_PASSPORT_COBRANDING_URL
Retrieves a string that contains a URL for a cobranding graphic provided by the Passport logon server. This option should be retrieved immediately after the logon server responds with a 401 status code. An application should pass in a buffer size, in bytes, that is big enough to hold the returned string.
WINHTTP_OPTION_PASSPORT_RETURN_URL
Sets a read-only option on a request handle that retrieves the Passport return URL.
WINHTTP_OPTION_PASSPORT_SIGN_OUT
Sets the option on a session handle to sign out of any Passport logins. An application should pass in the Passport return URL that was retrieved with WINHTTP_OPTION_PASSPORT_RETURN_URL. All cookies related to the return URL are cleared.
WINHTTP_OPTION_PASSWORD
Sets or retrieves a string value that contains the password associated with a request handle.
WINHTTP_OPTION_PROXY
Sets or retrieves an WINHTTP_PROXY_INFO structure that contains the proxy data on an existing session handle or request handle. When retrieving proxy data, an application must free the lpszProxy and lpszProxyBypass strings contained in this structure (if they are non-NULL) using the GlobalFree function. An application can query for the global proxy data (the default proxy) by passing a NULL handle.
WINHTTP_OPTION_PROXY_PASSWORD
Sets or retrieves a string value that contains the password used to access the proxy.
WINHTTP_OPTION_PROXY_SPN_USED
Gets the proxy Server Principal Name that WinHTTP supplied to SSPI during authentication. This string value is usefor passing to SspiPromptForCredentials after an authentication failure.
WINHTTP_OPTION_PROXY_USERNAME
Sets or retrieves a string value that contains the user name used to access the proxy.
WINHTTP_OPTION_QUIC_STATS
Retrieves a QUIC_STATISTICS structure that contains connection information such as RTT and bytes sent and received.
WINHTTP_OPTION_READ_BUFFER_SIZE
This option is deprecated; it has no effect.
WINHTTP_OPTION_RECEIVE_PROXY_CONNECT_RESPONSE
Sets whether or not the proxy response entity can be retrieved. This option is disabled by default.
WINHTTP_OPTION_RECEIVE_RESPONSE_TIMEOUT
Sets or retrieves an unsigned long integer value that contains the timeout value, in milliseconds, to wait to receive all response headers to a request. If WinHTTP fails to receive all the headers within this timeout period, the request is canceled. The default timeout value is 90 seconds.
This timeout is checked only when data is received from the socket. As a result, when the timeout expires the client application is not notified until more data arrives from the server. If no data arrives from the server, the delay between the timeout expiration and notification of the client application could be as large as the timeout value set using the dwReceiveTimeout parameter of the WinHttpSetTimeouts function.
WINHTTP_OPTION_RECEIVE_TIMEOUT
Sets or retrieves an unsigned long integer value that contains the time-out value, in milliseconds, to receive a partial response to a request or read some data. If the response takes longer than this time-out value, the request is canceled. The default timeout value is 30 seconds.
WINHTTP_OPTION_REDIRECT_POLICY
Sets the behavior of WinHTTP regarding the handling of a 30x HTTP redirect status code. This option can be set on a session or request handle to one of the following values:
| Term | Description |
|---|---|
| WINHTTP_OPTION_REDIRECT_POLICY_ALWAYS | All redirects are followed automatically. |
| WINHTTP_OPTION_REDIRECT_POLICY_DISALLOW_HTTPS_TO_HTTP | All redirects are followed, except those that originate from a secure (https) URL to an unsecure (http) URL. This is the default setting. |
| WINHTTP_OPTION_REDIRECT_POLICY_NEVER | Redirects are never followed. The 30x status is returned to the application. |
WINHTTP_OPTION_REJECT_USERPWD_IN_URL
Rejects URLs that contain a username and password. This option also rejects URLs that contain username:password semantics, even if no username or password is specified. For example, "u:p@hostname", ":@hostname", "u:@hostname", and ":p@hostname" would all be flagged as invalid. If an invalid URL is passed to the function, it returns ERROR_WINHTTP_INVALID_URL. This option is turned off by default.
WINHTTP_OPTION_REQUEST_ANNOTATION
Enables getting and setting a request annotation for the provided annotation name. That allows the caller to attach a string to the request for later retrieval to identify requests by whatever custom logic the caller finds useful.
WINHTTP_OPTION_REQUEST_PRIORITY
This option is deprecated; it has no effect.
WINHTTP_OPTION_REQUEST_STATS
Retreives statistics for the request. For a list of the available statistics, see WINHTTP_REQUEST_STATS.
WINHTTP_OPTION_REQUEST_TIMES
Retreives timing information for the request. For a list of the available timings, see WINHTTP_REQUEST_TIMES.
WINHTTP_OPTION_REQUIRE_STREAM_END
This option tells WinHttp to ignore "Content-Length" response headers, and continue receiving on a stream until the END_STREAM flag is received.
WINHTTP_OPTION_RESOLUTION_HOSTNAME
This option can be set on a WinHttp request handle before it has been sent. If set, WinHttp will use the caller-provided string as the hostname for DNS resolution.
WINHTTP_OPTION_RESOLVE_TIMEOUT
Sets or retrieves an unsigned long integer value that contains the time-out value, in milliseconds, to resolve a host name. The default timeout value is INFINITE. If a non-default value is specified, there is an overhead of one thread-creation per name resolution.
WINHTTP_OPTION_REVERT_IMPERSONATION_SERVER_CERT
Reverts any thread impersonation when building the server cert chain, forcing the use of the process token instead.
WINHTTP_OPTION_SECURE_PROTOCOLS
Sets an unsigned long integer value that specifies which Secure (HTTPS) protocols are acceptable. The default value for this setting varies by operating system version and may be impacted by installed updates.
- Windows 11. By default, only TLS1.2 and TLS1.3 are enabled.
- Windows 10, and Windows 8.1. By default, only SSL3, TLS1.0, TLS1.1, and TLS1.2 are enabled.
- Windows 8 and Windows 7. By default, only SSL3 and TLS1 are enabled.
The value can be a combination of one or more of the following values.
| Term | Description |
|---|---|
| WINHTTP_FLAG_SECURE_PROTOCOL_ALL | The Secure Sockets Layer (SSL) 2.0, SSL 3.0, and Transport Layer Security (TLS) 1.0 protocols can be used. |
| WINHTTP_FLAG_SECURE_PROTOCOL_SSL2 | The SSL 2.0 protocol can be used. |
| WINHTTP_FLAG_SECURE_PROTOCOL_SSL3 | The SSL 3.0 protocol can be used. |
| WINHTTP_FLAG_SECURE_PROTOCOL_TLS1 | The TLS 1.0 protocol can be used. |
| WINHTTP_FLAG_SECURE_PROTOCOL_TLS1_1 | The TLS 1.1 protocol can be used. |
| WINHTTP_FLAG_SECURE_PROTOCOL_TLS1_2 | The TLS 1.2 protocol can be used. |
| WINHTTP_FLAG_SECURE_PROTOCOL_TLS1_3 | The TLS 1.3 protocol can be used. |
If you need to enable support for newer protocols but are unable to recompile your application to use the appropriate values of WINHTTP_OPTION_SECURE_PROTOCOLS, then you can instead add the DefaultSecureProtocols registry entry. That registry entry allows you to specify which secure protocols should be used when the WINHTTP_OPTION_SECURE_PROTOCOLS option is not set.
Important
The instructions below involve modifying the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these instructions carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, see How to back up and restore the registry in Windows.
If an application does not call WinHttpSetOption(WINHTTP_OPTION_SECURE_PROTOCOLS), the system checks for the DefaultSecureProtocols registry entry and, if it's present, overrides the existing operating system defaults with the protocols specified in the DefaultSecureProtocols registry entry. The WinHTTP-specified protocols can be overruled by Secure Channel (Schannel) configuration settings that may disable protocols.
You can add the DefaultSecureProtocols registry entry in the following path:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\WinHttp
On x64-based computers, you must also add DefaultSecureProtocols to the Wow6432Node path:
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Internet Settings\WinHttp
The registry value is a DWORD bitmap. The value to use is determined by adding the values corresponding to the protocols desired.
| DefaultSecureProtocols value | Protocol enabled |
|---|---|
| 0x00000008 | Enable SSL 2.0 by default |
| 0x00000020 | Enable SSL 3.0 by default |
| 0x00000080 | Enable TLS 1.0 by default |
| 0x00000200 | Enable TLS 1.1 by default |
| 0x00000800 | Enable TLS 1.2 by default |
| 0x00002000 | Enable TLS 1.3 by default |
For example, if you want to override the default values for WINHTTP_OPTION_SECURE_PROTOCOLS to specify TLS 1.1 and TLS 1.2. In that case, take the value for TLS 1.1 (0x00000200) and the value for TLS 1.2 (0x00000800), add them together in calculator (in programmer mode), and the resulting registry value would be 0x00000A00.
WINHTTP_OPTION_SECURITY_CERTIFICATE_STRUCT
Retrieves the certificate for a SSL/TLS server into the WINHTTP_CERTIFICATE_INFO structure. The application must free the lpszSubjectInfo and lpszIssuerInfo members with LocalFree.
WINHTTP_OPTION_SECURITY_FLAGS
Sets or retrieves an unsigned long integer value that contains the security flags for a handle. It can be a combination of these values:
| Term | Description |
|---|---|
| SECURITY_FLAG_IGNORE_CERT_CN_INVALID | Allows an invalid common name in a certificate; that is, the server name specified by the application doesn't match the common name in the certificate. If this flag is set, the application doesn't receive a WINHTTP_CALLBACK_STATUS_FLAG_CERT_CN_INVALID callback. |
| SECURITY_FLAG_IGNORE_CERT_DATE_INVALID | Allows an invalid certificate date, that is, an expired or not-yet-effective certificate. If this flag is set, the application doesn't receive a WINHTTP_CALLBACK_STATUS_FLAG_CERT_DATE_INVALID callback. |
| SECURITY_FLAG_IGNORE_UNKNOWN_CA | Allows an invalid certificate authority. If this flag is set, the application doesn't receive a WINHTTP_CALLBACK_STATUS_FLAG_INVALID_CA callback. |
| SECURITY_FLAG_IGNORE_CERT_WRONG_USAGE | Allows the identity of a server to be established with a non-server certificate (for example, a client certificate). |
| SECURITY_FLAG_IGNORE_WEAK_SIGNATURE | Allows a weak signature to be ignored. This flag is available in the rollup update for each OS starting with Windows 7 and Windows Server 2008 R2. |
| SECURITY_FLAG_SECURE | Uses secure transfers. This is only returned in a call to WinHttpQueryOption. |
| SECURITY_FLAG_STRENGTH_MEDIUM | Uses medium (56-bit) encryption. This is only returned in a call to WinHttpQueryOption. |
| SECURITY_FLAG_STRENGTH_STRONG | Uses strong (128-bit) encryption. This is only returned in a call to WinHttpQueryOption. |
| SECURITY_FLAG_STRENGTH_WEAK | Uses weak (40-bit) encryption. This is only returned in a call to WinHttpQueryOption. |
WINHTTP_OPTION_SECURITY_INFO
Retreives the SChannel connection and cipher information for a request.
WINHTTP_OPTION_SECURITY_KEY_BITNESS
Retrieves an unsigned long integer value that contains the cipher strength of the encryption key. A larger number indicates stronger cipher strength encryption.
WINHTTP_OPTION_SEND_TIMEOUT
Sets or retrieves an unsigned long integer value that contains the time-out value, in milliseconds, to send a request or write some data. If sending the request takes longer than the timeout, the send operation is canceled. The default timeout is 30 seconds.
WINHTTP_OPTION_SERVER_CBT
Gets a pointer to SecPkgContext_Bindings structure that specifies a Channel Binding Token (CBT).
A Channel Binding Token is a property of a secure transport channel and is used to bind an authentication channel to the secure transport channel. This token can only be obtained by this option after an SSL connection has been established.
Note
Passing this option and a null value for lpBuffer to WinHttpQueryOption will return ERROR_INSUFFICIENT_BUFFER and the required byte size for the buffer in the lpdwBufferLength parameter. This returned buffer size value can be passed in a subsequent call to query for the Channel Binding Token. These steps are necessary when handling WINHTTP_CALLBACK_STATUS_REQUEST if you want to modify request headers based on the Channel Binding Token. Note that Windows XP and Vista do not support modifying request headers during this callback.
WINHTTP_OPTION_SERVER_CERT_CHAIN_CONTEXT
Retrieves the server certification chain context. WINHTTP_OPTION_SERVER_CERT_CHAIN_CONTEXT can be passed to obtain a duplicated pointer to the CERT_CHAIN_CONTEXT for a server certificate chain received during a negotiated SSL connection. The client must call CertFreeCertificateContext on the returned PCCERT_CONTEXT pointer that is filled into the buffer.
WINHTTP_OPTION_SERVER_CERT_CONTEXT
Retrieves the server certification context. WINHTTP_OPTION_SERVER_CERT_CONTEXT can be passed to obtain a duplicated pointer to the CERT CONTEXT for a server certificate received during a negotiated SSL connection. The client must call CertFreeCertificateContext on the returned PCCERT_CONTEXT pointer that is filled into the buffer.
WINHTTP_OPTION_SERVER_SPN_USED
Gets the server Server Principal Name that WinHTTP supplied to SSPI during authentication. This string value can be passed to SspiPromptForCredentials after an authentication failure.
WINHTTP_OPTION_SPN
Includes or removes the server port number when the SPN (service principal name) is built for Kerberos or Negotiate Kerberos authentication. This flag is one of the following values:
| Term | Description |
|---|---|
| WINHTTP_DISABLE_SPN_SERVER_PORT | Removes the server port number. |
| WINHTTP_ENABLE_SPN_SERVER_PORT | Includes the server port number. |
WINHTTP_OPTION_STREAM_ERROR_CODE
This option can be queried on a WinHttp request handle, and will return the error code indicated by a RST_STREAM frame received on an HTTP stream.
WINHTTP_OPTION_TCP_FAST_OPEN
Enables TCP Fast Open for the connection.
WINHTTP_OPTION_TCP_KEEPALIVE
This option can be set on a WinHttp session handle to enable TCP keep-alive behavior on the underlying socket. Takes a tcp_keepalive struct.
WINHTTP_OPTION_TLS_FALSE_START
Enables TLS False Start for the connection.
WINHTTP_OPTION_TCP_PRIORITY_STATUS
Query the hinted priority of the TCP socket set with WINHTTP_OPTION_TCP_PRIORITY_HINT. See the documentation for SIO_SET_PRIORITY_HINT for more details.
WINHTTP_OPTION_TLS_PROTOCOL_INSECURE_FALLBACK
This option can be set on a WinHttp session handle to control whether fallback to TLS 1.0 is allowed if there is a TLS handshake failure with a newer protocol version.
WINHTTP_OPTION_UNLOAD_NOTIFY_EVENT
Takes an event that will be set when the last callback has completed for a particular session. This flag must be must be used on a session handle. The event cannot be closed until after it has been set by WinHTTP.
WINHTTP_OPTION_UNSAFE_HEADER_PARSING
This option is reserved for internal use and should not be called.
WINHTTP_OPTION_UPGRADE_TO_WEB_SOCKET
Instructs the stack to start a WebSocket handshake process with WinHttpSendRequest. This option takes no parameters.
WINHTTP_OPTION_URL
Retrieves a string value that contains the full URL of a downloaded resource. If the original URL contained any extra data, such as search strings or anchors, or if the call was redirected, the URL returned differs from the original. The application should pass in a buffer, sized in bytes, that is big enough to hold the returned URL in wide char.
WINHTTP_OPTION_USE_GLOBAL_SERVER_CREDENTIALS
Takes a BOOL and can be set only a session handle. It will only propagate down to handles created from the session handle after the option has been set. If TRUE, this option causes as a last resort the use of global server credentials that were pushed down from WinInet. The default for this option is FALSE. This option requires registry key HKLM\Software\Microsoft\Windows\CurrentVersion\Internet Settings!ShareCredsWithWinHttp. This registry key is not present by default. When it is set, WinINet will send credentials down to WinHTTP. Whenever WinHttp gets an authentication challenge and if there are no credentials set on the current handle, it will use the credentials provided by WinINet.
WINHTTP_OPTION_USE_SESSION_SCH_CRED
Allows setting a single credential to use by default for all endpoints within the session instead of having per-endpoint default credentials. That might improve performance by reducing credential management overhead. Note that this default credential will have no effect when a client certificate is explicitly provided.
WINHTTP_OPTION_USER_AGENT
Sets or retrieves the user agent string on handles supplied by WinHttpOpen and used in subsequent WinHttpSendRequest functions, as long as it is not overridden by a header added by WinHttpAddRequestHeaders or WinHttpSendRequest. When retrieving a user agent, the application should pass in a buffer, sized in bytes, that is big enough to hold the returned URL in wide char. When setting the user agent, the buffer size is the length of the string, in characters, plus the NULL terminator.
WINHTTP_OPTION_USERNAME
Sets or retrieves a string that contains the user name.
WINHTTP_OPTION_WEB_SOCKET_CLOSE_TIMEOUT
Sets the time, in milliseconds, that WinHttpWebSocketClose should wait to complete the close handshake. The default is 10 seconds.
WINHTTP_OPTION_WEB_SOCKET_KEEPALIVE_INTERVAL
Sets the interval, in milliseconds, to send a keep-alive packet over the connection. The default interval is 30000 (30 seconds). The minimum interval is 15000 (15 seconds). Using WinHttpSetOption to set a value lower than 15000 will return with ERROR_INVALID_PARAMETER.
Note
The default value for WINHTTP_OPTION_WEB_SOCKET_KEEPALIVE_INTERVAL is read from HKLM:\SOFTWARE\Microsoft\WebSocket\KeepaliveInterval. If a value is not set, the default value of 30000 will be used. It is not possible to have a lower keepalive interval than 15000 milliseconds.
WINHTTP_OPTION_WEB_SOCKET_RECEIVE_BUFFER_SIZE
Sets or retrieves a DWORD which specifies the receive buffer size to be used on WebSocket connections.
WINHTTP_OPTION_WEB_SOCKET_SEND_BUFFER_SIZE
Sets or retrieves a DWORD which specifies the send buffer size to be used on WebSocket connections.
WINHTTP_OPTION_WORKER_THREAD_COUNT
Sets an unsigned long integer value that specifies the number of worker threads the thread pool should use for asynchronous completions. The default value of this option is zero, which specifies that the number of worker threads is equal to the number of CPUs on the system. This option can only be set on a NULL HINTERNET handle before an asynchronous operation has occurred. This option can only be set once.
Applies to: Windows 7 and later; Windows Server 2008 R2 and later.
WINHTTP_OPTION_WRITE_BUFFER_SIZE
This option is deprecated; it has no effect.
Remarks
The following table lists the option flags by specifying which handles they can act upon, whether they can be queried and set, and the data type used. An "X" indicates that the option flag is valid for use with the function or handle, while a "-" specifies that the option flag is invalid.
Attempting to set or query an option flag on a Windows version where it is not supported will result in ERROR_WINHTTP_INVALID_OPTION.
| Option flag, and data type | Session handle | Request handle | Query option | Set option | Minimum Windows Version |
|---|---|---|---|---|---|
| WINHTTP_OPTION_ASSURED_NON_BLOCKING_CALLBACKS BOOL |
X | - | - | X | - |
| WINHTTP_OPTION_AUTOLOGON_POLICY DWORD |
- | X | - | X | - |
| WINHTTP_OPTION_BACKGROUND_CONNECTIONS DWORD |
X | - | - | X | Windows 10 Version 21H1 |
| WINHTTP_OPTION_CALLBACK LPVOID |
X | X | X | X | - |
| WINHTTP_OPTION_CLIENT_CERT_CONTEXT CERT_CONTEXT |
- | X | - | X | Windows Vista |
| WINHTTP_OPTION_CLIENT_CERT_ISSUER_LIST SecPkgContext_IssuerListInfoEx |
- | X | X | - | Windows Vista |
| WINHTTP_OPTION_CODEPAGE DWORD |
X | - | - | X | - |
| WINHTTP_OPTION_CONFIGURE_PASSPORT_AUTH DWORD |
X | - | - | X | - |
| WINHTTP_OPTION_CONNECT_RETRIES DWORD |
X | X | X | X | - |
| WINHTTP_OPTION_CONNECT_TIMEOUT DWORD |
X | X | X | X | - |
| WINHTTP_OPTION_CONNECTION_INFO WINHTTP_CONNECTION_INFO |
- | X | X | - | - |
| WINHTTP_OPTION_CONNECTION_STATS_V0 TCP_INFO_v0 |
- | X | X | - | Windows 10 Version 1903 |
| WINHTTP_OPTION_CONNECTION_STATS_V1 TCP_INFO_v1 |
- | X | X | - | Windows 10 Version 2004 |
| WINHTTP_OPTION_CONTEXT_VALUE DWORD_PTR |
X | X | X | X | - |
| WINHTTP_OPTION_DECOMPRESSION DWORD |
X | X | - | X | Windows 8.1 |
| WINHTTP_OPTION_DISABLE_CERT_CHAIN_BUILDING BOOL |
X | - | - | X | Windows 10 Version 21H1 |
| WINHTTP_OPTION_DISABLE_FEATURE DWORD |
- | X | - | X | - |
| WINHTTP_OPTION_DISABLE_SECURE_PROTOCOL_FALLBACK BOOL |
X | - | - | X | Windows 10 Version 1903 |
| WINHTTP_OPTION_DISABLE_STREAM_QUEUE BOOL |
X | X | - | X | Windows 10 Version 1809 |
| WINHTTP_OPTION_ENABLE_FEATURE DWORD |
* | * | - | X | - |
| WINHTTP_OPTION_ENABLE_HTTP_PROTOCOL DWORD |
X | X | - | X | Windows 10 Version 1607 |
| WINHTTP_OPTION_ENABLE_HTTP2_PLUS_CLIENT_CERT_CONTEXT BOOL |
X | - | - | X | Windows 10 Version 21H1 |
| WINHTTP_OPTION_ENABLETRACING DWORD |
- | - | X | X | - |
| WINHTTP_OPTION_ENCODE_EXTRA BOOL |
X | X | - | X | Windows 10 Version 1803 |
| WINHTTP_OPTION_EXPIRE_CONNECTION N/A |
- | X | - | X | Windows 10 Version 1903 |
| WINHTTP_OPTION_EXTENDED_ERROR DWORD |
X | X | X | - | - |
| WINHTTP_OPTION_FIRST_AVAILABLE_CONNECTION BOOL |
X | - | - | X | Windows 10 Version 21H1 |
| WINHTTP_OPTION_GLOBAL_PROXY_CREDS WINHTTP_CREDS |
X | X | - | X | - |
| WINHTTP_OPTION_GLOBAL_SERVER_CREDS WINHTTP_CREDS_EX |
X | X | - | X | - |
| WINHTTP_OPTION_HANDLE_TYPE DWORD |
X | X | X | - | - |
| WINHTTP_OPTION_HTTP_PROTOCOL_REQUIRED BOOL |
X | X | - | X | Windows 10 Version 1903 |
| WINHTTP_OPTION_HTTP_PROTOCOL_USED DWORD |
- | X | X | - | Windows 10 Version 1607 |
| WINHTTP_OPTION_HTTP_VERSION HTTP_VERSION_INFO |
X | X | X | X | - |
| WINHTTP_OPTION_HTTP2_KEEPALIVE DWORD |
X | - | - | X | Windows 10 Version 21H1 |
| WINHTTP_OPTION_HTTP2_PLUS_TRANSFER_ENCODING BOOL |
X | X | - | X | Windows 10 Version 21H1 |
| WINHTTP_OPTION_IGNORE_CERT_REVOCATION_OFFLINE BOOL |
- | X | - | X | Windows 10 Version 2004 |
| WINHTTP_OPTION_IPV6_FAST_FALLBACK BOOL |
X | - | - | X | Windows 10 Version 1903 |
| WINHTTP_OPTION_IS_PROXY_CONNECT_RESPONSE BOOL |
X | X | X | - | - |
| WINHTTP_OPTION_MAX_CONNS_PER_1_0_SERVER DWORD |
X | - | X | X | - |
| WINHTTP_OPTION_MAX_CONNS_PER_SERVER DWORD |
X | - | X | X | - |
| WINHTTP_OPTION_MAX_HTTP_AUTOMATIC_REDIRECTS DWORD |
X | X | X | X | - |
| WINHTTP_OPTION_MAX_HTTP_STATUS_CONTINUE DWORD |
X | X | X | X | - |
| WINHTTP_OPTION_MAX_RESPONSE_DRAIN_SIZE DWORD |
X | X | X | X | - |
| WINHTTP_OPTION_MAX_RESPONSE_HEADER_SIZE DWORD |
X | X | X | X | - |
| WINHTTP_OPTION_PARENT_HANDLE HINTERNET |
X | X | X | - | - |
| WINHTTP_OPTION_PASSPORT_COBRANDING_TEXT LPWSTR |
- | X | X | - | - |
| WINHTTP_OPTION_PASSPORT_COBRANDING_URL LPWSTR |
- | X | X | - | - |
| WINHTTP_OPTION_PASSPORT_RETURN_URL LPVOID |
- | X | X | - | - |
| WINHTTP_OPTION_PASSPORT_SIGN_OUT LPVOID |
X | - | - | X | - |
| WINHTTP_OPTION_PASSWORD LPWSTR |
- | X | X | X | - |
| WINHTTP_OPTION_PROXY WINHTTP_PROXY_INFO |
X | X | X | X | - |
| WINHTTP_OPTION_PROXY_PASSWORD LPWSTR |
- | X | X | X | - |
| WINHTTP_OPTION_PROXY_SPN_USED LPWSTR |
- | X | X | - | - |
| WINHTTP_OPTION_PROXY_USERNAME LPWSTR |
- | X | X | X | - |
| WINHTTP_OPTION_READ_BUFFER_SIZE DWORD |
- | X | X | X | - |
| WINHTTP_OPTION_RECEIVE_PROXY_CONNECT_RESPONSE BOOL |
X | X | - | X | - |
| WINHTTP_OPTION_RECEIVE_RESPONSE_TIMEOUT DWORD |
X | X | X | X | - |
| WINHTTP_OPTION_RECEIVE_TIMEOUT DWORD |
X | X | X | X | - |
| WINHTTP_OPTION_REDIRECT_POLICY DWORD |
X | X | X | X | - |
| WINHTTP_OPTION_REJECT_USERPWD_IN_URL BOOL |
- | X | - | X | - |
| WINHTTP_OPTION_REQUEST_PRIORITY DWORD |
- | X | X | X | - |
| WINHTTP_OPTION_REQUEST_STATS WINHTTP_REQUEST_STATS |
- | X | X | - | Windows 10 Version 1903 |
| WINHTTP_OPTION_REQUEST_TIMES WINHTTP_REQUEST_TIMES |
- | X | X | - | Windows 10 Version 1903 |
| WINHTTP_OPTION_REQUIRE_STREAM_END BOOL |
X | X | - | X | Windows 10 Version 21H1 |
| WINHTTP_OPTION_RESOLUTION_HOSTNAME LPWSTR |
- | X | - | X | Windows 10 Version 21H1 |
| WINHTTP_OPTION_RESOLVE_TIMEOUT DWORD |
X | X | X | X | - |
| WINHTTP_OPTION_SECURE_PROTOCOLS DWORD |
X | - | - | X | - |
| WINHTTP_OPTION_SECURITY_CERTIFICATE_STRUCT WINHTTP_CERTIFICATE_INFO |
- | X | X | - | - |
| WINHTTP_OPTION_SECURITY_FLAGS DWORD |
- | X | X | X | - |
| WINHTTP_OPTION_SECURITY_INFO WINHTTP_SECURITY_INFO |
- | X | X | - | Windows 10 Version 2004 |
| WINHTTP_OPTION_SECURITY_KEY_BITNESS DWORD |
- | X | X | - | - |
| WINHTTP_OPTION_SEND_TIMEOUT DWORD |
X | X | X | X | - |
| WINHTTP_OPTION_SERVER_CBT SecPkgContext_Bindings* |
- | X | X | - | - |
| WINHTTP_OPTION_SERVER_CERT_CHAIN_CONTEXT CERT_CHAIN_CONTEXT |
- | X | X | - | Windows 10 Version 2004 |
| WINHTTP_OPTION_SERVER_CERT_CONTEXT CERT CONTEXT |
- | X | X | - | - |
| WINHTTP_OPTION_SERVER_SPN_USED LPWSTR |
- | X | X | - | - |
| WINHTTP_OPTION_SPN DWORD |
- | X | - | X | - |
| WINHTTP_OPTION_STREAM_ERROR_CODE DWORD |
- | X | X | - | Windows 10 Version 21H1 |
| WINHTTP_OPTION_TCP_FAST_OPEN BOOL |
X | - | - | X | Windows 10 Version 2004 |
| WINHTTP_OPTION_TCP_KEEPALIVE tcp_keepalive |
X | - | - | X | Windows 10 Version 2004 |
| WINHTTP_OPTION_TLS_FALSE_START BOOL |
X | - | - | X | Windows 10 Version 2004 |
| WINHTTP_OPTION_TLS_PROTOCOL_INSECURE_FALLBACK BOOL |
X | - | - | X | Windows 10 Version 21H1 |
| WINHTTP_OPTION_UNLOAD_NOTIFY_EVENT HINTERNET |
X | - | - | X | - |
| WINHTTP_OPTION_UNSAFE_HEADER_PARSING DWORD |
- | X | - | X | - |
| WINHTTP_OPTION_UPGRADE_TO_WEB_SOCKET N/A |
- | X | - | X | - |
| WINHTTP_OPTION_URL LPWSTR |
- | X | X | - | - |
| WINHTTP_OPTION_USE_GLOBAL_SERVER_CREDENTIALS BOOL |
X | X | - | X | - |
| WINHTTP_OPTION_USER_AGENT LPWSTR |
X | - | X | X | - |
| WINHTTP_OPTION_USERNAME LPWSTR |
- | X | X | X | - |
| WINHTTP_OPTION_WEB_SOCKET_CLOSE_TIMEOUT DWORD |
- | - | X | X | - |
| WINHTTP_OPTION_WEB_SOCKET_KEEPALIVE_INTERVAL DWORD |
- | - | X | X | - |
| WINHTTP_OPTION_WEB_SOCKET_RECEIVE_BUFFER_SIZE DWORD |
X | X | X | X | Windows 8.1 |
| WINHTTP_OPTION_WEB_SOCKET_SEND_BUFFER_SIZE DWORD |
X | X | X | X | Windows 8.1 |
| WINHTTP_OPTION_WORKER_THREAD_COUNT DWORD |
- | - | - | X | - |
| WINHTTP_OPTION_WRITE_BUFFER_SIZE DWORD |
- | X | X | X | - |
Note
For Windows XP and Windows 2000, see Run-Time Requirements.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows XP, Windows 2000 Professional with SP3 [desktop apps only] |
| Minimum supported server | Windows Server 2003, Windows 2000 Server with SP3 [desktop apps only] |
| Redistributable | WinHTTP 5.0 and Internet Explorer 5.01 or later on Windows XP and Windows 2000. |
| Header | Winhttp.h |