Romain Dillet, writing for TechCrunch;
Apple just released a new beta of iOS 11 ahead of the final iOS 11 release in September. Things are still quite rough and I wouldn’t recommend installing the beta on a production device just yet. You don’t want to risk having your phone become useless.
The beta 4 is only available if you’re a registered developer for now. While Apple also has a public beta program, the company usually waits a few days before releasing new developer betas in the public beta channel.