Apple Pushes Out Rare Second iOS 17.1 Release Candidate
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In a relatively uncommon occurrence, Apple has made a new build of its iOS 17.1 Release Candidate (RC) available ahead of the public iOS 17.1 release, which is expected to land on October 24.
Usually, Apple only sends out a single Release Candidate at the end of each iOS beta cycle to provide developers and public beta testers with an early look. That RC version is ultimately identical to what gets released to the public — hence the name “Release Candidate.”
However, even though everything should be fully baked by the time an RC update is sent out, sometimes the wider distribution or a Release Candidate results in the discovery of a serious bug that requires Apple to make some adjustments before the public release.
That’s what seems to have happened in this case. However, it’s likely the problem only impacts the iPhone 15 lineup since those are the only models receiving the new iOS 17.1 RC build, which now features a build number of 21B77 — a minor increment from the 21B74 sent out earlier this week.
It’s unclear what kind of problem was encountered, as the release notes for the new RC don’t provide any insight; the update features the same notes as the prior 21B74 RC build, which will be included in the final iOS 17.1 public release next week — regardless of which build it turns out to be.
While secondary RC builds sometimes happen, they’re pretty rare and usually mean that somebody found a show-stopping problem with the first RC that couldn’t wait for a later patch release — which, in this case, would be an iOS 17.1.1 update.
Nevertheless, it’s also possible Apple engineers found a minor issue that was easily tweaked before the final release. Nevertheless, in principle, software engineering teams are usually reluctant to make changes after an RC is sent out since that creates the possibility of other unintended side effects.
One theory is that the new iOS 17.1 “RC2” could fix the seemingly random overnight shutdown problems that quite a few iPhone 15 users have reported. However, these don’t seem to be exclusive to the iPhone 15 models; I’ve encountered this problem on my iPhone 14 Pro Max (although not this week), and there have been other reports of older iPhones shutting down on the iOS 17.1 betas.
The only other iPhone 15-specific changes included in iOS 17.1 are a reported fix for a “screen burn-in” issue that seems limited to the iPhone 15 Pro Max. The release notes for the first iOS 17.1 RC build noted that it “fixes an issue that may cause display image persistence.” However, we haven’t seen any confirmation from developers or beta testers whether that’s actually the case, so perhaps Apple still needed to polish that last piece up.
It’s also possible that iOS 17.1 RC introduced an entirely new issue specific to the iPhone 15, in which case it would make sense for the company’s software engineers to roll back whatever is causing that issue before the public release of iOS 17.1 creates a potential problem for millions of iPhone 15 owners worldwide.
Either way, it’s unlikely we’ll ever know for sure what’s changed in the 21B77 RC or iPhone 15 users, but all older iOS 17-compatible iPhones remain happily on the 21B74 build. We’ll have to wait and see whether that’s what gets pushed out on Tuesday or if Apple distributes 21B77 or a later build for all devices just to keep things consistent.
