It happened fast. One minute you could track your blood oxygen levels on the latest Apple Watch, and the next, a massive legal battle with a company called Masimo effectively neutered the world's most popular wearable. If you go to an Apple Store right now in the United States to buy a Series 10 or an Ultra 2, that little red light—the Apple Watch oxygen sensor—is technically there, but it won't do a thing. It’s disabled. Dead software in a living device.
It’s a weird situation.
Honestly, it’s frustrating for users who bought the watch specifically for health tracking. You’re paying full price for hardware that has been "lobotomized" because of an intellectual property dispute. But the story isn't just about lawyers and patents; it’s about how we measure health at home and whether these wrist-based sensors actually tell us anything useful in the first place.
The Messy Reality of the Apple Watch Oxygen Sensor Ban
Let's look at what actually happened. Joe Kiani, the CEO of a medical tech company named Masimo, claimed Apple stole their pulse oximetry technology after meetings that were supposed to be about a partnership. Apple, being Apple, denied it. The International Trade Commission (ITC) eventually sided with Masimo. This led to a ban on importing watches with that specific tech. To keep selling watches in the US, Apple had to release a software update that permanently deactivates the Apple Watch oxygen sensor on any new units sold after January 18, 2024.
If you have an older watch, like a Series 6, 7, or 8, you're fine. Your sensor still works. If you bought your Ultra 2 before the cutoff, you're also in the clear. But for everyone else? You're looking at a greyed-out icon.
It’s worth noting that this is a very "American" problem. If you hop across the border to Canada or fly to London, the sensors on the shelves there work perfectly. The hardware is identical. It’s a software lock tied to the model number of watches destined for the US market. Some people have tried using VPNs or changing their region settings to get it back, but Apple is smarter than that. The block is baked into the device’s hardware identifier. You can't just "trick" it back into existence.
Does the SpO2 Sensor Even Matter for Most People?
Here is the kicker: medical professionals have always been a bit skeptical of wrist-based pulse oximetry.
When you go to a hospital, they put a clip on your finger. That’s because light travels through your finger to a sensor on the other side (transmissive oximetry). The Apple Watch oxygen sensor uses reflective oximetry. It shines a light into your wrist and measures what bounces back off your skin and blood vessels. It’s inherently less accurate. If your watch band is loose, or if you have dark tattoos on your wrist, or if you’re just cold and your blood vessels have constricted, the reading can be way off.
Still, for people with sleep apnea or those heading to high altitudes, having a "good enough" baseline is better than nothing. It's about trends, not single data points. If your blood oxygen—usually called $SpO_2$—is consistently hitting 95% to 100%, you're golden. If you see it dipping into the 80s while you sleep, that’s a "talk to your doctor" moment, even if the sensor isn't "medical grade."
The loss of this feature isn't just a minor inconvenience; it’s a gap in the "Proactive Health" ecosystem Apple has been building for a decade.
How to Tell if Your Watch is Neutered
If you’re buying a used watch or a refurbished one, you might be wondering if you’re getting the "real" version or the "restricted" version. There is a specific way to check.
Go into the Settings app on the watch, then General, then About. Look for the Model Number. Models that end in LL/A are the US versions. But more specifically, Apple started using a different part number suffix for the "non-oxygen" versions. You can also just open the Blood Oxygen app. If it says "The Blood Oxygen app is no longer available," well, there is your answer.
Interestingly, the Apple Watch oxygen sensor is still physically present in the Series 10. Apple didn't redesign the hardware to remove the LEDs. They just "flipped a switch" in the code. This suggests that if Apple ever settles with Masimo—which would likely cost hundreds of millions, if not billions—they could theoretically re-enable the feature with a simple watchOS update. But don't hold your breath. Apple is stubborn. They'd rather fight in court for five years than pay a licensing fee they think is unfair.
What Users Are Doing Instead
Since the ban, people have been getting creative.
Some are intentionally seeking out "New Old Stock" (NOS) from third-party retailers like B&H or smaller shops that still have inventory from before January 2024. Others are looking toward competitors. The Garmin Venu 3 or the Samsung Galaxy Watch 7 (if you're on Android) both offer robust blood oxygen tracking without the legal drama.
Then there are the purists. They just buy a $20 finger pulse oximeter from a pharmacy. It’s more accurate anyway. It doesn't sync with your Apple Health charts automatically, which sucks for data nerds, but it gives you the number you need when you feel short of breath or sick.
The Technical Hurdle: Why This Tech is Hard to Mimic
You might ask: "Why can't Apple just write new code?"
The problem is that Masimo’s patents cover the fundamental way the sensor filters out "noise." When you move your arm, the blood sloshes around. That movement creates interference. Masimo’s "Signal Extraction Technology" (SET) is the gold standard for ignoring that movement and finding the true pulse. Apple’s version was allegedly too close to that secret sauce.
To fix it without Masimo, Apple has to invent a completely new way to process the light signals that doesn't infringe on those patents. That’s a massive engineering lift. You can't just "code around" physics.
Actionable Steps for Apple Watch Buyers
If you are in the market for a health-tracking wearable right now, here is exactly how you should navigate the Apple Watch oxygen sensor mess:
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- Check the SKU: If you are buying a Series 9, Ultra 2, or Series 10 in the US from a major retailer (Apple, Best Buy, Target), assume the oxygen sensor is disabled.
- Look for Refurbished Units: Older refurbished models (Series 7 or 8) through reputable sites like Back Market or Amazon's renewed program often still have working sensors because they were manufactured and sold before the legal ruling took effect.
- Prioritize the Vitals App: Even without the active oxygen sensor, the new Vitals app in watchOS 11 still tracks heart rate, respiratory rate, and wrist temperature. For many users, these metrics are actually more predictive of illness than a spot-check of blood oxygen.
- Don't Buy for Sleep Apnea Detection Alone: While the Series 10 markets "Sleep Apnea Notifications," it actually uses the accelerometer to track "Breathing Disturbances" rather than the oxygen sensor. You don't actually need the SpO2 sensor for this specific new feature, which is a clever workaround by Apple's engineers.
- Consider Global Versions: If you travel frequently, buying an Apple Watch in a country like Canada or Japan will give you a fully functional device. Just be aware that warranty support can be a nightmare if you need a repair back in the US.
The tech world moves fast, and while the Apple Watch oxygen sensor is currently a casualty of a corporate war, the underlying hardware remains a marvel. For now, the best move is to understand that "New" doesn't always mean "More Features." Sometimes, it means fewer.
Decide if that 2% difference in oxygen saturation is worth the hunt for an older model or if you're okay with Apple's other health metrics doing the heavy lifting. Most people find that the heart rate and sleep tracking are enough to get a clear picture of their wellness, even if the red light stays dark for the foreseeable future.