WebRTC Videochat and Conferencing Support

WebRTC is a new real time video communication technology with limited support.

Regular Browser Support

WebRTC is not currently supported by default PC browsers (Internet Explorer for Windows and Safari for Mac OS). This creates a real issue for organisation networks with standard software distributions, studios and internet caffes with restrictive administrative software or plain newbie users that use their computers with default setup.
WebRTC is not currently supported on default mobile browsers either,  excepting latest Android.
While WebRTC is popular with technology geeks and enthusiasts, many regular users are not able to access such implementation or can use only limited functionality.

For more details see these reference sites:

PC Browser Share WebRTC RTMP
Internet Explorer + Edge (Windows default) 9% No* Yes
Safari (MacOS default) 13% No Yes
Chrome 57% Yes Yes
Firefox 9% Yes* Yes
Opera 5% Yes Yes

*Mozilla reports Navigator.getUserMedia as Deprecated and MediaDevices.getUserMedia as Experimental .
*IE does not support WebRTC at all but there are plans to introduce some support in Edge browser .

PC Browser market share shows WebRTC setup will not work for a lot of PC users due to browser support. Many of these users with default browsers are beginners or restricted by workplace policies from using a different browsers and are unlikely to change their browser.
On mobiles WebRTC support is even lower while RTMP is supported both on Android and iOS with apps.
RTMP streams can be published to iOS and Android browsers as HLS.

WebRTC vs RTMP

Currently, WebRTC is still in development discussion for its complete implementation whereas RTMP is already available for any Real Time Communication project’s deployments.

WebRTC could be a solution for the future and RTMP is a solution for the present that could be required for a while.

WebRTC could loose the current battle for its standardisation and interoperability, with many implementation proposals over the top web browsers or with a divergent market approach from Google, Microsoft, Apple.

Relayed (RTMP Server) vs P2P (WebRTC or Flash RTMFP)

Depending on ISP and network setup an important share of users can’t connect and stream directly to each other at all. Some experience huge latency (several seconds) and massive frame loss over P2P.

Test your P2P network capabilities with this  RTMFP Connectivity checker .

Using a relay server is most reliable solution for video communications.

Some providers say only 8% of their users need RTMP but that could be biased considering they emphasise WebRTC / RTMFP sessions that don’t require streaming server costs.
Usually most home internet connections don’t go well with P2P unless users are in same or very close network.

Security Concerns with Using Browsers that Support WebRTC

In January 2015, TorrentFreak reported that browsers supporting WebRTC suffer from a serious security flaw that compromises the security of VPN-tunnels, by allowing the true IP address of the user to be read. The IP address read requests are not visible in the browsers developer console, and they are not blocked by common ad blocking/privacy plugins (enabling online tracking by advertisers and other entities despite precautions).

If your browser is WebRTC compliant test this IP detection tool.