Question: Is there any free social login modules (for twitter and facebook) available for drupal 8? I have checked OpenID Connect module, but it does not support facebook and twitter logins. Please advice, if there are any stable modules available for this.

Thanks,

Answer: 
You can use oneAll social login. It covers 25+ social networks and works well. Download [here](https://www.drupal.org/project/social_login)
For facebook login module in d8 you can use <https://www.drupal.org/project/simple_fb_connect>

For twitter login <https://www.drupal.org/project/twitter>.
But twitter module is in dev version so it is not functional yet.You can take inspiration from d7 version and try to upgrade