Apple released iOS 18.6.1 on Wednesday, 14 August 2025, at 10:00 PST (19:00 SAST).
What is iOS 18.6.1 and who can get it?
The update is available for iPhones made from 2018 onwards. This includes the iPhone XS, iPhone XR, and every model released since, such as the iPhone 11, iPhone 12, iPhone 13, iPhone 14, iPhone 15, and the latest iPhone 16 series.
It also covers the second- and third-generation iPhone SE models.
To download iOS 18.6.1, users need to:
- go to the Settings app on their iPhone;
- select General; and
- then choose Software Update.
The download is around 720MB, which means it may take a few minutes depending on internet speed.
Why is iOS 18.6.1 important?
This update is not just about bug fixes. It brings back a feature that had been disabled for millions of Apple Watch owners in the United States: Blood Oxygen monitoring.
In simple terms, Blood Oxygen monitoring measures the amount of oxygen in your blood. This is important because it can give clues about your breathing, heart health, and overall wellbeing.
Normally, Apple Watches like the Series 9 and Ultra 2 could do these checks directly on the watch.
However, due to a legal dispute with medical device company Masimo, Apple had to turn off the feature on some US models.
The newly released iOS 18.6.1 and watchOS 11.6.1 updates restore the function, but in a slightly different way.
How the new Blood Oxygen feature works
Instead of the Apple Watch doing the full calculation itself, the process now works with the iPhone. Users can still open the Blood Oxygen app on the watch, but the raw data is sent to the iPhone, which processes it and shows the results in the Health app, under the “Respiratory” section.
This workaround means that the feature is once again usable for:
- Apple Watch Series 7
- Apple Watch Series 8
- Apple Watch Series 9
- Apple Watch Series 10
- Apple Watch Ultra
- Apple Watch Ultra 2
This change ensures users in the United States are not left behind compared to Apple Watch users in other countries.
What about security fixes?
Interestingly, Apple did not publish any official security fixes or CVEs (Common Vulnerabilities and Exposures) tied to iOS 18.6.1.
Normally, CVEs list security issues patched in updates. The absence suggests this release is focused almost entirely on restoring the Blood Oxygen feature rather than addressing new security risks.
Should you update?
Apple strongly recommends that all users install iOS 18.6.1, even if they don’t own an Apple Watch.
This ensures that devices remain up to date with Apple’s software changes and prevents possible compatibility issues with future updates.
For Apple Watch owners in the U.S., especially those with Series 9, Series 10, and Ultra 2 models, this update is essential.
It brings back an important health tracking tool that many people rely on.