What is an active pen/stylus?

An active pen (available only for compatible devices) is a special stylus that allows for more natural handwriting. Usually an active pen supports:

  • pressure sensitive input
  • differentiating between pen and finger touch
  • one or more side buttons
  • detecting the pen hovering above the display
  • eraser tip on some active pens

Using an active pen with Squid allows for:

  • pressure sensitive (natural) handwriting
  • write with the pen, erase with your finger ¹
  • palm rejection by ignoring finger/hand touch when the pen is in range
  • hold the pen side button and flick left/right to undo/redo ²
  • hold the pen side button and flick up/down to access the tool picker/color picker  ²
  • use an alternate tool while holding the pen side button ¹ ²
  • erase using the opposite end of the pen ¹ ³

¹ Configurable in the Squid settings. 

² Unfortunately, the side button functionality does not work on Chromebooks.

³ Available on active pens with an eraser tip.

Active Pen Enabled Devices

Device manufacturers often have a branded active pen that is compatible with their devices. Some active pens can be used across devices from different manufacturers. This is because they use the same underlying active pen technology. There are currently three major active pen technologies for Android and Chromebooks: USI, EMR, and AES.

Universal Stylus Initiative (USI)

A USI pen/stylus is powered by a replaceable battery (e.g. AAAA), a rechargeable battery, or a capacitor. There are many popular USI pens and USI-capable devices, most of which are Chromebooks and ChromeOS tablets.

Wacom EMR

A Wacom EMR pen/stylus is powered wirelessly when near the screen of an EMR-capable device and does not require a battery or internal power source. Popular Wacom EMR pens include:

Popular Wacom EMR-capable devices include:

Wacom AES

A Wacom AES pen/stylus is powered by a replaceable battery (e.g. AAAA), a rechargeable battery, or a capacitor. Popular Wacom AES pens include:

    • Pixelbook Pen
    • HP Chromebook x2 Pen
    • Lenovo Active Pen 2

Popular Wacom AES-capable devices include:

    • Pixelbook
    • Pixel Slate
    • HP Chromebook x2


The NVIDIA DirectStylus is a passive stylus that has some functionality similar to an active pen.

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