I have used IMO app and it is worthless app.First of all its features are hackneyed and look up is absolutely bogus .I downloaded it as I had heard it offered free video calling .Later I discovered or realised that it is good for nothing as it is not popular .It does not download and install easily although it requires less space. if you chat it does not show whether another user is online or offline. then voice quality is very minimal and picture quality is horrible.
The picture shivers and stands still due to buffering. There is no understanding when your online friend visited for the last time. I have not been able to transfer a single file or picture .If anyone call you and you are offline there is no remedy to understand that someone called you.Its a paltry, worthless, trivial, footling app.I am no way to recommend .whats app and messenger are far better