If you’ve built an application using the old Web Browser Control (mshtml, aka Internet Explorer), you might notice that by default it does not support HTTP/2. For instance, a trivial WebOC host loading Akamai’s HTTP2 test page:

When your program is running on any build of Windows 10, you can set a Feature Control Key with your process’ name to opt-in to using HTTP/2.

For applications running at the OS-native bitness, write the key here:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main\FeatureControl\FEATURE_WEBOC_ENABLE_HTTP2

For 32-bit applications running on 64-bit Windows, write it here:
HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\Internet Explorer\Main\FeatureControl\FEATURE_WEBOC_ENABLE_HTTP2

Like so:

After you make this change and restart the application, it will use HTTP/2 if the server and network path supports it.

Using HTTP/2 should help improve performance and can even resolve functional bugs.

-Eric