A large English speaking American based site.

Free to sign up. Free to practice, learn and teach. Entry to formal competitions charged in BBO$ purchased on the site.

You usually play with real people, but you can hire robots.

There are some excellent videos on Youtube showing how to register, to logon, to play in the practice area, and how the alerting works (it's a bit different). Go to Youtube and search "Bridge Base Online" plus whatever topic.

English Bridge Union runs competitions, as do many larger EBU Affiliated Clubs.

BBO plays under World Bridge Federation (WBF) rules. There is no announcing; this an English Bridge Union (EBU) idea.

This means that conventional bids should be alerted.

On the BBO site, unlike at the table, a player alerts their own bids. The alert and information given is not visible to partner.
Once you get used it, particularly remembering to set up the alert before you bid, it's actually quite good, if strange.

Click here for a YouTube video showing you how.

Click here for a Facebook posted video, you need to fast forward to 40 minutes in.