In my six years as a technology writer, I've reviewed a lot of great laptops and tablets, a lot of which have touchscreens and support pen input. I love the versatility a good stylus can bring to a device, but there's one thing that's always bugged me about them. Depending on which laptop or tablet you buy, you'll likely need a different kind of pen. While the Universal Stylus Initiative (USI) exists to try and unify things, there are a lot of other standards in use on Windows laptops, and a lot of them aren't compatible with each other. It can get quite confusing if you're shopping for a pen. So, let's attempt to explain them all.

Why are there so many pen types

I'll start by diving into Wacom EMR pens. This is a widely known pen type that you'll see most commonly on Samsung Galaxy Book devices. This list of devices also includes the old Surface Pro 1 and Surface Pro 2. It differs from the other types in that it offers a pen-to-paper feel thanks to electromagnetic resonance (EMR) technology, which means there's a layer of sensors that sits behind the device’s LCD screen and glass. There's no need for the pen to have an external power source since everything lives on the screen.

But wait, there's more! There are also Wacom AES pens. Some of the best Lenovo Yoga laptops use this standard. AES pens differ from EMR pens because they work with displays that contain sensors with multiple electrostatic grids. The pen connects with one of these grids to generate a response, which means the tech can pinpoint where the pen is located. You'll also get palm rejection and better sensitivity as bonuses. Unlike EMR, this type of pen needs a power source for charging. AES pens also don't work with devices that use EMR pens because of the screen layer difference.

And adding to the confusion? There are both AES 2.0 and AES 1.0 pens. Devices with AES 2.0 digitizers support both 1.0 and 2.0, but older devices with AES 1.0 digitizers only support 1.0 pens.

Elsewhere, there's MPP and N-Trig technology. N-Trig used to stand on its own as a pen type, but Microsoft now owns the company. It fused N-Trig together with its own Surface Pen to create the MPP standard back in 2016 in the hopes of reducing pen incompatibility between N-Trig and Wacom. MPP is now in use on many tablets, including Microsoft's own Surface series, but also the HP Spectre and HP Envy lines. MPP is most similar to AES, which means the pen needs a power source but works via Bluetooth connectivity. I'll also briefly mention the Apple Pencil, which works with the company's iPads, and the S Pen, which only works with Samsung devices and runs on a version of EMR.

Finally, there's the Universal Stylus Initiative (USI). The goal of this organization is to develop the new USI standard that'll work across devices and make it easier for users to start using styli. Many new Chromebooks are using it, and partners like Google, Dell, LG, and Lenovo have all signed on to be member companies of the standard. But it's still mainly in use on Chromebooks. I have yet to see these pens on Windows devices. So it's not quite "universal" just yet.

Trying to make sense of it all

Looking at this all, there is some interoperability here, but not much, and there's more need for it in the future. MPP styli seem to be the best of the bunch right now, and while not all OEMs use it, there is some cross-compatibility. Dell's Active Stylus, for example, works on devices that support both the MPP and AES pen protocols. However, that doesn't apply to all pens, as you can't take a Surface Pen and use it on a regular laptop that uses EMR or AES technology.

However, USI is doing great things. It's set to ensure that you can use a single stylus across all your devices, but it's not as mainstream or on Windows devices yet. You'll still see devices with AES, EMR, and MPP.

It's time these OEMs wake up and take USI seriously and stop the confusion. Because honestly, all of these different protocols make trying to find a stylus a mess. And if I feel this way, I'm sure you do, too.