Devise limit one session per user at a time

You can't do it.

• You can control IP addresses of user, so you can prevent presence of user from two IP at a time. ANd you can bind login and IP. You can try to check cities and other geolocation data through IP to block user.
• You can set cookies to control something else.

But none of this will guarantee that only one user uses this login, and that those 105 IP from all over the world doesn't belong to only one unique user, which uses Proxy or whatever.

And the last: you never need this in the Internet.

UPD

However, what I'm asking is about limiting multiple users from using the same account simultaneously which I feel should be possible

So you can store some token, that will contain some encrypted data: IP + secret string + user agent + user browser version + user OS + any other personal info: encrypt(IP + "some secret string" + request.user_agent + ...). And then you can set a session or cookie with that token. And with each request you can fetch it: if user is the same? Is he using the same browser and the same browser version from the same OS etc.

Also you can use dynamic tokens: you change token each request, so only one user could use system per session, because each request token will be changed, another user will be logged out as far as his token will be expired.

This gem works well: https://github.com/devise-security/devise-security

Add to Gemfile

gem 'devise-security'

after bundle install

rails generate devise_security:install

Then run

rails g migration AddSessionLimitableToUsers unique_session_id

Edit the migration file

class AddSessionLimitableToUsers < ActiveRecord::Migration
  def change
    add_column :users, :unique_session_id, :string, limit: 20
  end
end

Then run

rake db:migrate

Edit your app/models/user.rb file

class User < ActiveRecord::Base
  devise :session_limitable # other devise options
  ... rest of file ...
end

Done. Now logging in from another browser will kill any previous sessions. The gem actual notifies the user that he is about to kill a current session before logging in.