question

@Afrojkhan Pathan First, I would be remiss if I did not mention of promote the RingCentral Video Client SDK, as it is designed to help people embed video meetings directly in their application WITHOUT an iframe. Using this, you can build the exact experience you want, have people login to your own application prior to joining (as opposed to logging in via RingCentral). Check it out:

https://developers.ringcentral.com/guide/video/client-sdk

Another thing to try is to modify the display attribute of your OAuth login URL. See permissible values here: https://developers.ringcentral.com/api-reference/Authorization

Or perhaps OAuth is not really what you should be doing at all? If you are embedding RCV into an iframe, then that is just a web session. As long as the user is logged into v.ringcentral.com, then when you embed the same URL into an iframe, the user's session will have already been established and logging in won't be necessary. So the question becomes, how can I log someone in prior to rendering the iframe?

The Client SDK will be the best tool in this scenario, but it will require you to host the front end of the meeting, and deploy a React app (check out the sample app) if you want to take advantage of the ready-made UI components.