Note: Advice in this article will only work for DotNetBrowser 1.
See the corresponding article for DotNetBrowser 2 here.

DotNetBrowser inherits Chromium Plugin Architecture.

In the lightweight mode DotNetBrowser can display only windowless plugins. Windowless plugins are designed to run directly within the rendering pipeline. Right now only Flash and Silverlight supports windowless mode, so they can be displayed by DotNetBrowser.

Note: Since version 1.7, NPAPI plugins are no longer supported. If you have to use NPAPI plugins, we recommend that you stick to DotNetBrowser versions up to 1.6.4

Testing PPAPI plugins compatibility

The Chromium switch --register-pepper-plugins can be used for temporary registration of the plugin.

--register-pepper-plugins="[full_path]\ppapi_tests.dll#PPAPI Tests##1.2.3;application/x-ppapi-tests"

Running .dll plugins is not a supported way to ship to your users. It's fine for testing only.