Ubisoft plans to run a closed beta for ahead of its release, and you can guarantee yourself access by preordering a copy of the shooter.
The closed beta will be available on all platforms--, , and --and is set to take place "sometime after" the end of the PC-only closed alpha. The beta will include more content and be better polished than the alpha, which we recently got a look at .
"The Closed Alpha and the Closed Beta will help us to build a stable experience and to playtest game elements on a very large scale," reads a post on the . "Whether you're testing early on PC during the closed alpha, or helping us validate the experience once we open on all platforms, we’re looking forward to interacting with you and working together to make Tom Clancy's Rainbow Six Siege the best it can be at launch."
If you've already preordered Siege, you'll still get a beta code prior to its launch. In the meantime, you can still if you haven't already done so.
Ubisoft has published a offering more details on the beta and how it differs from the alpha. A key point is that the alpha is much more limited in the number of people who will be allowed in, and its focus is on dealing with bugs and server stability.