Mobile user set moderator by default

How can I set mobile user as moderator by default when join meeting.

It depends on how your installation is configured. If you join a meeting on you will always be a moderator, every user is.

suppose 3 user has joined meeting but 2 are from web and 1 from mobile . what I want that 1 user has joined from phone then this user will be moderator always…
how can I do this.

Are you hosting your own Jitsi application? If so, you can implement secure domain and just have that user on a mobile device authenticate as moderator. This of course is assuming that it’s the same user all the time. If not, you can still use secure domain, create a user and provide whoever is joining on a mobile device with the credentials to log in as moderator. So, the login credentials will be more role-based than user-based; this way, different people can use the same login credentials.

How I get user has joined from mobile and remaining are from web

It doesn’t matter where the user comes from, the authentication mechanism you enable in your server applies to everyone. You could enable basic authentication and allow guests, in that case the web participants would need to wait for a moderator to enter the room first. The moderator could be web or mobile, doesn’t matter, but it would need to provide a username and password. Or you could use a JWT token.

You cannot decide this from the app.