The Apple Watch Series 9 and Apple Watch Ultra 2 have been living on borrowed time in the US after both were found to infringe on patents owned by rival health technology company Masimo. The US International Trade Commission (ITC) ordered a ban on the sale of both in October that came into effect on Christmas Day. However, Apple managed to get a temporary reprieve from the US Court of Appeals for the Federal Circuit, which ordered an interim stay on the ban while it waited to hear counter-arguments from the ITC on why a longer ban shouldn’t be granted while the case awaits its appeal hearing.

In the end, the Court of Appeals agreed with the ITC’s position that Apple’s arguments were unconvincing and the ban should remain in effect until and unless the courts decide to overturn the ITC ruling entirely — a case that could take a year or more to be resolved.

The good news is that Apple had a backup plan to keep the Apple Watch Series 9 and Ultra 2 on sale. By disabling the blood oxygen measuring technology at a software level, it convinced US Customs and Border Protection that these modified Apple Watch models no longer infringed on the patents ruled on by the ITC and can, therefore, remain on sale in the US.

How to Tell Which Apple Watch Models Have Disabled Blood Oxygen Sensors

First, it’s important to note that Apple is not required to disable the blood oxygen sensor in any Apple Watch model that’s already been sold — even if it was sold only last night before the ban came back into effect.

This means you don’t need to worry about a future watchOS update suddenly breaking your blood oxygen monitoring features. Apple has presumably tagged the “modified” Apple Watches in some way to ensure that older models won’t get the same software updates.

This also means that any Apple Watch purchased before today (January 18, 2024) should still have the Blood Oxygen Sensor fully enabled like it’s been since it was first introduced on the Apple Watch Series 6 in 2020.

Along the same lines, any Apple Watch purchased from Apple from today onward — whether from an Apple retail store or the Apple Store online — will have the blood oxygen sensor disabled. Apple has pulled all the other ones from its shelves, as it’s legally required by do under the ITC’s cease and desist order (CDO), which is now back in effect.

Although this is very straightforward if you’re buying an Apple Watch Series 9 or Apple Watch Ultra 2 directly from Apple, it’s somewhat murkier with third-party retailers and will get even more confusing as time goes on.

For example, if you walk into a Best Buy today, you’ll likely still be able to buy an Apple Watch with the Blood Oxygen Monitoring feature. However, that may not be the case in a few weeks or months.

This is because the ITC’s CDO to stop selling the Apple Watch only applies to Apple. Third-party retailers like Amazon, Best Buy, Walmart, and others are under no obligation to stop selling the Apple Watch with its blood oxygen sensor fully enabled. Third-party retailers can continue selling whatever Apple Watches they already have on hand, even if they have working blood oxygen sensors.

However, the ITC has also banned the infringing Apple Watch models from being imported into the United States by anyone and prohibited Apple from helping third-party retailers sell the infringing devices. Hence, once these retailers run out of whatever inventory they have, the only new models they’ll be able to receive from Apple will have the blood oxygen sensor disabled.

Fortunately, Apple has made it fairly easy to distinguish between a standard Apple Watch Series 9 or Apple Watch Ultra 2 and one that’s been “modified” to remove the blood oxygen monitoring capabilities.

Apple has added a note in the fine print at the bottom of the Apple Watch Series 9 page and on Apple’s Identify your Apple Watch support document noting that the “new” Apple Watch models in the US will have a distinctive part number to set them apart from those that still include the blood oxygen feature.

The ability to measure Blood Oxygen is no longer available on Apple Watch units sold by Apple in the United States on or after January 18, 2024. These are indicated with part numbers ending in LW/A.

A standard Apple Watch Series 9 or Apple Watch Ultra 2 sold in the United States typically ends with the part number LL/A. This is a country-specific suffix used in the part numbers for nearly all Apple products manufactured for sale in the US and even some in Canada.

Other one- and two-letter codes are used for other countries, such as “J” for Japan, “B” for the UK, “LE” for Argentina, and so forth. There’s not a lot of rhyme or reason for these, but “LW” is not on the list, so Apple has chosen to use it to set the “modified” Apple Watch units apart from the original ones. Since the ban only applies in the US, that’s also the only place the “LW” code will need to be used.

Avoid the “W”

Like every Apple product, you can find the part number on the back of the Apple Watch box. The part number should start with an “M” and is distinct from the “model” number, which begins with an A and refers to an entire family of Apple Watches with the same internal hardware and basic design.

For instance, model A2980 covers all 45mm Apple Watch Series 9 GPS-only models, while MR9C3LL/A would represent one with a Midnight Aluminum Case packaged with the Midnight Sport Loop, and MR983LL/A would be the same model in Starlight.

These are the part numbers you’ll see if you look closely at most US online retailers today — other than Apple, of course. However, as these retailers exhaust their existing stock, they’ll likely be resupplied with the same ones that Apple is now selling — those without the blood oxygen sensor enabled. At that point, you should see part numbers like MR9C3LW/A and MR983LW/A appearing in the listings.

While Apple hasn’t said anything official, it’s likely that the company doesn’t plan to leave these blood oxygen monitoring features disabled forever. Should it prevail in its appeal with the ITC or otherwise find a way to reactivate the feature without infringing on Masimo’s patents, it will likely release a software update for the “LW” models that will reactivate blood oxygen monitoring in some way. The hardware pulse oximetry sensors are still in the devices — in fact, they’re likely identical to the Apple Watch Series 9 and Ultra 2 models that have been sold before today — they’re merely blocked in software in some way.