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
Update: Windows’ Internet Control Panel has a “HTTP2” checkbox, but it only controls web platform apps (IE and Legacy Edge), and unfortunately, the setting does not work properly for AppContainer/LowIL processes, which enable HTTP2 by default. This means that the checkbox, as of Windows 10 version 1909, is pretty much useless for its intended purpose (as only Intranet Zone sites outside of Protected Mode run at MediumIL).
A bug has been filed.
Update: Users of the new Chromium-based Edge browser can launch an instance with HTTP2 disabled using the disable-http2 command line argument, e.g. ms-edge.exe --disable-http2.
I’m not aware of a straightforward way to disable HTTP2 for the new Chromium-Edge-based WebView2 control, which has HTTP2 enabled by default.
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