The HTS221 is an inexpensive humidity sensor which makes it great for everyday measurement applications. The device lets the user choose between a 3-wire SPI or the ever-popular I2C, which only needs two wires for data. If the user decides to use I2C, the SparkFun Qwiic compatible STEMMA QT connectors are included so there is no need to solder. Since the HTS221 is a super small 2mm square, it has been put in a breakout board with level shifting and a power regulator. This makes it easy to use on a breadboard with either a 5V logic level device like a Metro 328 or Arduino Uno, or with 3.3V logic level devices like a Feather M4 or Raspberry Pi of the user's choice.