Runtime configuration options for networking

HTTP/2 protocol

• Configures whether support for the HTTP/2 protocol is enabled.

• Introduced in .NET Core 3.0.

• .NET Core 3.0 only: If you omit this setting, support for the HTTP/2 protocol is disabled. This is equivalent to setting the value to false.

• .NET Core 3.1 and .NET 5+: If you omit this setting, support for the HTTP/2 protocol is enabled. This is equivalent to setting the value to true.

	Setting name	Values
runtimeconfig.json	System.Net.Http.SocketsHttpHandler.Http2Support	false - disabled true - enabled
Environment variable	DOTNET_SYSTEM_NET_HTTP_SOCKETSHTTPHANDLER_HTTP2SUPPORT	0 - disabled 1 - enabled

This configuration setting doesn't have a specific MSBuild property. However, you can add a RuntimeHostConfigurationOption MSBuild item instead. Use the runtimeconfig.json setting name as the value of the Include attribute. For an example, see MSBuild properties.

SPN creation in HttpClient (.NET 6 and later)

• Impacts generation of service principal names (SPN) for Kerberos and NTLM authentication when Host header is missing and target is not running on default port.
• .NET Core 2.x and 3.x do not include port in SPN.
• .NET Core 5.x does include port in SPN
• .NET 6 and later versions don't include the port, but the behavior is configurable.

	Setting name	Values
runtimeconfig.json	System.Net.Http.UsePortInSpn	true - includes port number in SPN, for example, HTTP/host:port false - does not include port in SPN, for example, HTTP/host
Environment variable	DOTNET_SYSTEM_NET_HTTP_USEPORTINSPN	1 - includes port number in SPN, for example, HTTP/host:port 0 - does not include port in SPN, for example, HTTP/host

This configuration setting doesn't have a specific MSBuild property. However, you can add a RuntimeHostConfigurationOption MSBuild item instead. Use the runtimeconfig.json setting name as the value of the Include attribute. For an example, see MSBuild properties.

UseSocketsHttpHandler (.NET Core 2.1-3.1 only)

• Configures whether System.Net.Http.HttpClientHandler uses System.Net.Http.SocketsHttpHandler or older HTTP protocol stacks (WinHttpHandler on Windows and CurlHandler, an internal class implemented on top of libcurl, on Linux).

  Note

  You may be using high-level networking APIs instead of directly instantiating the HttpClientHandler class. This setting also affects which HTTP protocol stack is used by high-level networking APIs, including HttpClient and HttpClientFactory.

• If you omit this setting, HttpClientHandler uses SocketsHttpHandler. This is equivalent to setting the value to true.

	Setting name	Values
runtimeconfig.json	System.Net.Http.UseSocketsHttpHandler	true - enables the use of SocketsHttpHandler false - enables the use of WinHttpHandler on Windows or libcurl on Linux
Environment variable	DOTNET_SYSTEM_NET_HTTP_USESOCKETSHTTPHANDLER	1 - enables the use of SocketsHttpHandler 0 - enables the use of WinHttpHandler on Windows or libcurl on Linux

Note

Starting in .NET 5, the System.Net.Http.UseSocketsHttpHandler setting is no longer available.

Latin1 headers (.NET Core 3.1 only)

• This switch allows relaxing the HTTP header validation, enabling SocketsHttpHandler to send ISO-8859-1 (Latin-1) encoded characters in headers.

• If you omit this setting, an attempt to send a non-ASCII character will result in HttpRequestException. This is equivalent to setting the value to false.

	Setting name	Values
runtimeconfig.json	System.Net.Http.SocketsHttpHandler.AllowLatin1Headers	false - disabled true - enabled
Environment variable	DOTNET_SYSTEM_NET_HTTP_SOCKETSHTTPHANDLER_ALLOWLATIN1HEADERS	0 - disabled 1 - enabled

Note

This option is only available in .NET Core 3.1 since version 3.1.9, and not in previous or later versions. In .NET 5 we recommend using RequestHeaderEncodingSelector.