These macros allow users to determine which version of this document is supported by the headers defined by the specification. All headers in this document shall define the __cpp_lib_experimental_net feature test macro in Table [tab:info.features].
If an implementation supplies all of the conditionally-supported features specified in [conformance.conditional], all headers in this document shall additionally define the __cpp_lib_experimental_net_extensible feature test macro.
| Macro name | Value |
| __cpp_lib_experimental_net | 201803 |
| __cpp_lib_experimental_net_extensible | 201803 |