The HTML5 pipeline is currently experimental. Some projects may not run properly when built for the HTML5 platform. Expect some rough edges.
You can find them in Engine/Source/ThirdParty/HTML5/emsdk/, but no configuration or additional installation is required to deploy to HTML5.
A 64-bit browser is currently required to run HTML5 builds.
Download Firefox nightlies
Download Chromium builds
Once they are installed, you can select the browser to launch your map in from the Launch dropdown menu.
To test a packaged HTML5 project:
Select HTML5 from the Package Project fly-out menu.
Once the project has packaged, open the destination location and run HTML5LaunchHelper.
Note the localhost address from this window.
Open [Localhost Address]/[ProjectName].html in your 64-bit browser. For example, http://localhost:8000/MyProject.html using the above localhost address with a project named MyProject.