Raspberry Pi Pico W

Specifications:
The main chip on board is the RP2040 made by Raspberry Pi (their first in-house microcontroller chip!) and is a dual-core ARM Cortex M0+ processor, with a flexible clock running up to 133MHz. WiFi is enabled via the use of an Infineon CYW43439.

RP2040 microcontroller chip designed by Raspberry Pi in the United Kingdom
Dual-core ARM Cortex M0+ processor, flexible clock running up to 133 MHz
264kB of SRAM, and 2MB of onboard Flash memory
Infineon CYW43439 wireless chip
IEEE 802.11n wireless LAN
Bluetooth 5.2 (not software supported at launch)
WPA3
SoftAP (up to 4 clients)
Onboard antenna licenced from ABRACON (connected via SPI to the RP2040)
Castellated module allows soldering directly to carrier boards
USB 1.1 Host and Device support
Low-power sleep and dormant modes
Drag & drop programming using mass storage over USB
26 multi-function GPIO pins
2×SPI, 2×I2C, 2×UART, 3×12-bit ADC, 16×controllable PWM channels
Real-time clock (RTC)
Temperature sensor
Accelerated floating-point libraries on-chip
8×Programmable IO (PIO) state machines for custom peripheral support
Dimensions (WxLxH)
Pico W: 21mm x 51.3mm x 3.9mm
Weight Pico W: 4g