Pinout

MicroSD card module (SPI) pinout

Pins

GND
VCC (5V on the common blue modules — they carry a 3.3V regulator and level shifter; bare purple boards are 3.3V only)
MISO
MOSI
SCK
CS
Card must be FAT16/FAT32 (SD library); SPI mode tops out well below the card rating — fine for logging

Pins	6: GND, VCC, MISO, MOSI, SCK, CS
Supply	5 V (regulated modules), 3.3 V (bare boards)
Card logic	3.3 V, level shifted on 5 V modules
Interface	SPI, mode 0
Max SPI clock	25 MHz (card), 8 MHz on an Arduino Uno
File system	FAT16 / FAT32 (Arduino SD library)
Card capacity	Up to 32 GB (SDHC, FAT32)
Libraries	SD, SdFat

The order GND VCC MISO MOSI SCK CS from the left, socket on top, is that of the common HW-125 board. Other modules reorder the header (many put CS first), so match the silk on your board, not this list.

USB Type-A / Type-BContacts: 4 (USB 2.0), 9 (USB 3.x); Bus voltage: 5 V; Current (standard port): 500 mA (USB 2.0), 900 mA (USB 3.x)
3.5mm audio jack (TRS)Contacts: 2 (TS), 3 (TRS), 4 (TRRS); Plug diameter: 3.5 mm; Stereo pinout: Tip left, ring right, sleeve ground
Ethernet (RJ45, T568B)Contacts: 8 (8P8C); Contact pitch: 1.02 mm; Pairs used: 2 pairs (10/100BASE-T, pins 1-2, 3-6), 4 pairs (1000BASE-T)
HDMI (Type A, 19 pins)Contacts: 19; Video signals: 3 TMDS data pairs + 1 clock pair; Max bandwidth: 10.2 Gbit/s (1.3/1.4), 18 Gbit/s (2.0), 48 Gbit/s (2.1)
Micro-HDMI (Type D, 19 pins)Contacts: 19 (numbered differently from Type A); Contact pitch: 0.4 mm; Plug size: ≈ 6.4 × 2.8 mm
VGA (DE-15)Contacts: 15 in 3 rows (DE-15 high density); Video signals: Analog R, G, B, 0.7 V peak-to-peak into 75 Ω; Sync: Separate H and V sync, TTL level
USB-C (receptacle, key pins)Contacts: 24 (receptacle); Contact pitch: 0.5 mm; Plug size: 8.25 × 2.4 mm, reversible
USB Type-C (USB-PD capable receptacle)Contacts: 24 (receptacle); Default VBUS: 5 V until a PD contract is negotiated; PD fixed voltages (SPR): 5, 9, 15, 20 V