If you thought iOS 18.6 was the final stop before iOS 19, Apple has proven otherwise. The tech giant has quietly released iOS 18.6.1, a surprise update for iPhones. Unlike many previous updates, this release does not focus on security patches or bug fixes but instead introduces a major change that directly benefits Apple Watch users. Specifically, the update restores a long-missing health feature—blood oxygen monitoring—that was disabled in the U.S. following a legal dispute.
So, should you install iOS 18.6.1 right away? Let’s break down what this update does, who it’s for, and what users are saying about it.
Apple has made iOS 18.6.1 available for all iPhones released from 2018 onwards. That means if you own an iPhone XS, iPhone XS Max, or iPhone XR, or any later model, you can download and install the update. This includes the:
iPhone 11 series
iPhone 12 series
iPhone 13 series
iPhone 14 series
iPhone 15 series
iPhone 16 series (including the iPhone 16e)
iPhone SE (2nd and 3rd generation)
To update, simply go to Settings > General > Software Update, then select Download and Install. The update is about 720MB, which is considered a medium-sized download. Installation should only take a few minutes, depending on your Wi-Fi speed and available storage.
Why Was iOS 18.6.1 Released?
iOS 18.6.1 does not come with any new security fixes, in contrast to most releases. Its main objective is to bring back a revamped blood oxygen feature for specific Apple Watch users in the United States.
A patent fight between Apple and the medical technology startup Masimo was the beginning of it all. The International Trade Commission (ITC) declared in 2023 that Apple’s blood oxygen sensors violated Masimo’s patents. Consequently, Apple was forced to disable the feature on the Apple Watch Series 9 and Apple Watch Ultra 2 models sold in the United States. Additionally, the more recent Apple Watch Series 10 does not come with blood oxygen functionality.
Thanks to a recent U.S. Customs ruling, Apple has now found a workaround. The iOS 18.6.1 update, along with watchOS 11.6.1, allows Apple Watch users to reaccess blood oxygen readings—but in a slightly different way.
How the Redesigned Blood Oxygen Feature Works
Previously, blood oxygen measurements were calculated directly on the Apple Watch. With iOS 18.6.1, that process has changed. Here’s what happens now:
- You open the Blood Oxygen app on your Apple Watch.
- The watch’s sensors collect the raw oxygen data.
- Instead of calculating results on the watch, the data is transferred to your iPhone.
- The paired iPhone, running iOS 18.6.1, performs the calculation.
- Results are displayed in the Health app under the Respiratory section.
This clever approach allows Apple to comply with the legal ruling while still providing users with access to one of the most popular health-tracking features.
Which Apple Watches Are Compatible?
Not every Apple Watch supports this feature. The redesigned blood oxygen monitoring is available on:
Apple Watch Series 7
Apple Watch Series 8
Apple Watch Series 9
Apple Watch Ultra
Apple Watch Ultra 2
Apple Watch Series 10 (with paired iPhone update)
If you own one of these models in the U.S., you’ll need both iOS 18.6.1 on your iPhone and watchOS 11.6.1 on your Apple Watch to unlock the feature.
What Apple Says About the Update
Apple emphasized that its health features are developed with privacy and scientific research at the core. The company highlighted that in addition to blood oxygen monitoring, Apple Watch still offers:
ECG app
Irregular rhythm notifications
Sleep apnea notifications
Fall detection
Sleep tracking
Wrist temperature sensing
The Vitals app
Noise monitoring
Medications reminders
Mindfulness tools
In short, iOS 18.6.1 helps ensure Apple Watch users in the U.S. regain access to one of the device’s standout health features without losing any of the other wellness tools.
User Reactions So Far
The majority of initial responses to iOS 18.6.1 have been favorable. Some iPhone owners have reported that their devices are “snappier” and have observed a minor improvement in overall performance. Crucially, since the implementation, no widespread defects or difficulties have been reported.
Although one Redditor reported that their iPad was displaying a blank screen, this seems unconnected given there is currently no iPadOS version of this update available. All things considered, installing the update seems risk-free.
Should You Upgrade to iOS 18.6.1?
The short answer: Yes.
Here’s why:
If you’re in the U.S. and own a compatible Apple Watch, iOS 18.6.1 restores blood oxygen monitoring, making it a must-have update.
Even if you don’t use an Apple Watch, there’s no downside. The update doesn’t remove any features and may slightly improve performance.
Since there are no security patches this time, you don’t have to rush—but updating ensures compatibility with future watchOS releases.
For Apple Watch owners, don’t forget to install watchOS 11.6.1 along with iOS 18.6.1 to enable the feature fully.
Final Thoughts
Apple’s decision to release iOS 18.6.1 is a rare move, but it highlights how seriously the company takes its health features. By introducing this workaround, Apple ensures that millions of Apple Watch users in the U.S. can once again access blood oxygen monitoring—a feature that many people rely on for health tracking.
While the update may seem minor compared to major iOS releases, it’s a smart fix to a complicated legal challenge. If you have a compatible iPhone, it’s worth installing iOS 18.6.1 today.
FAQs
It’s a surprise iPhone update released by Apple in August 2025, designed mainly to restore blood oxygen monitoring for Apple Watch users in the U.S.
No. Apple confirmed that this update does not include new security patches.
Yes. While it primarily benefits Apple Watch users, the update is safe to install and may improve iPhone performance slightly.