For best results here is a list of browsers that are compatible with WebRTC:
No plugins are required. All you need is the latest version of your preferred browser.
Here are the links to instructions on how to update to the latest version for each browser:
Chrome - https://support.google.com/chrome/answer/95414?hl=en&co=GENIE.Platform%3DDesktop&oco=1
Firefox - https://support.mozilla.org/en-US/kb/update-firefox-latest-version
Opera - https://techhelpkb.com/how-to-update-opera-web-browser/
Android - https://support.google.com/nexus/answer/4457705?hl=en