When flag 0x2000 is set, the 32-bit word at offset 28 of each
block is a family ID naming the chip family the
firmware is for, and a bootloader ignores blocks for any other family. The master list is
utils/uf2families.json in Microsoft’s uf2 repository; the table
below gives all 80 entries in the list’s own order, with its short names and
descriptions. In a file the ID is stored little-endian: 0xE48BFF56 appears
as 56 FF 8B E4.
Family IDs
| ID | Short name | Description |
|---|---|---|
0x16573617 | ATMEGA32 | Microchip (Atmel) ATmega32 |
0x1851780a | SAML21 | Microchip (Atmel) SAML21 |
0x1b57745f | NRF52 | Nordic NRF52 |
0x1c5f21b0 | ESP32 | ESP32 |
0x1e1f432d | STM32L1 | ST STM32L1xx |
0x202e3a91 | STM32L0 | ST STM32L0xx |
0x21460ff0 | STM32WL | ST STM32WLxx |
0x22e0d6fc | RTL8710B | Realtek AmebaZ RTL8710B |
0x2abc77ec | LPC55 | NXP LPC55xx |
0x300f5633 | STM32G0 | ST STM32G0xx |
0x31d228c6 | GD32F350 | GD32F350 |
0x3379CFE2 | RTL8720D | Realtek AmebaD RTL8720D |
0x04240bdf | STM32L5 | ST STM32L5xx |
0x4c71240a | STM32G4 | ST STM32G4xx |
0x4fb2d5bd | MIMXRT10XX | NXP i.MX RT10XX |
0x51e903a8 | XR809 | Xradiotech 809 |
0x53b80f00 | STM32F7 | ST STM32F7xx |
0x55114460 | SAMD51 | Microchip (Atmel) SAMD51 |
0x57755a57 | STM32F4 | ST STM32F4xx |
0x5a18069b | FX2 | Cypress FX2 |
0x5d1a0a2e | STM32F2 | ST STM32F2xx |
0x5ee21072 | STM32F1 | ST STM32F103 |
0x621e937a | NRF52833 | Nordic NRF52833 |
0x647824b6 | STM32F0 | ST STM32F0xx |
0x675a40b0 | BK7231U | Beken 7231U/7231T |
0x68ed2b88 | SAMD21 | Microchip (Atmel) SAMD21 |
0x6a82cc42 | BK7251 | Beken 7251/7252 |
0x6b846188 | STM32F3 | ST STM32F3xx |
0x6d0922fa | STM32F407 | ST STM32F407 |
0x4e8f1c5d | STM32H5 | ST STM32H5xx |
0x6db66082 | STM32H7 | ST STM32H7xx |
0x70d16653 | STM32WB | ST STM32WBxx |
0x7b3ef230 | BK7231N | Beken 7231N |
0x7eab61ed | ESP8266 | ESP8266 |
0x7f83e793 | KL32L2 | NXP KL32L2x |
0x8fb060fe | STM32F407VG | ST STM32F407VG |
0x9fffd543 | RTL8710A | Realtek Ameba1 RTL8710A |
0xada52840 | NRF52840 | Nordic NRF52840 |
0x820d9a5f | NRF52820 | Nordic NRF52820_xxAA |
0xbfdd4eee | ESP32S2 | ESP32-S2 |
0xc47e5767 | ESP32S3 | ESP32-S3 |
0xd42ba06c | ESP32C3 | ESP32-C3 |
0x2b88d29c | ESP32C2 | ESP32-C2 |
0x332726f6 | ESP32H2 | ESP32-H2 |
0x540ddf62 | ESP32C6 | ESP32-C6 |
0x3d308e94 | ESP32P4 | ESP32-P4 |
0xf71c0343 | ESP32C5 | ESP32-C5 |
0x77d850c4 | ESP32C61 | ESP32-C61 |
0xb6dd00af | ESP32H21 | ESP32-H21 |
0x9e0baa8a | ESP32H4 | ESP32-H4 |
0x3101f7c1 | ESP32S31 | ESP32-S31 |
0xde1270b7 | BL602 | Boufallo 602 |
0xe08f7564 | RTL8720C | Realtek AmebaZ2 RTL8720C |
0xe48bff56 | RP2040 | Raspberry Pi RP2040 |
0xe48bff57 | RP2XXX_ABSOLUTE | Raspberry Pi Microcontrollers: Absolute (unpartitioned) download |
0xe48bff58 | RP2XXX_DATA | Raspberry Pi Microcontrollers: Data partition download |
0xe48bff59 | RP2350_ARM_S | Raspberry Pi RP2350, Secure Arm image |
0xe48bff5a | RP2350_RISCV | Raspberry Pi RP2350, RISC-V image |
0xe48bff5b | RP2350_ARM_NS | Raspberry Pi RP2350, Non-secure Arm image |
0x00ff6919 | STM32L4 | ST STM32L4xx |
0x9af03e33 | GD32VF103 | GigaDevice GD32VF103 |
0x4f6ace52 | CSK4 | LISTENAI CSK300x/400x |
0x6e7348a8 | CSK6 | LISTENAI CSK60xx |
0x11de784a | M0SENSE | M0SENSE BL702 |
0x4b684d71 | MaixPlay-U4 | Sipeed MaixPlay-U4(BL618) |
0x9517422f | RZA1LU | Renesas RZ/A1LU (R7S7210xx) |
0x2dc309c5 | STM32F411xE | ST STM32F411xE |
0x06d1097b | STM32F411xC | ST STM32F411xC |
0x72721d4e | NRF52832xxAA | Nordic NRF52832xxAA |
0x6f752678 | NRF52832xxAB | Nordic NRF52832xxAB |
0xa0c97b8e | AT32F415 | ArteryTek AT32F415 |
0x699b62ec | CH32V | WCH CH32V2xx and CH32V3xx |
0x7b8c32a7 | CH32V4X7 | WCH CH32V407 and CH32V467 |
0x7be8976d | RA4M1 | Renesas RA4M1 |
0x7410520a | MAX32690 | Analog Devices MAX32690 |
0xd63f8632 | MAX32650 | Analog Devices MAX32650/1/2 |
0xf0c30d71 | MAX32666 | Analog Devices MAX32665/6 |
0x91d3fd18 | MAX78002 | Analog Devices MAX78002 |
0x7d7a66ef | PY32F071-UVK5-V3 | Quansheng UV-K5 V3 amateur radio based on Puya Semiconductor PY32F071 |
0xf4b47471 | Adaboot | Adafruit maintained MCUboot+UF2 bootloader that manages board checks using extension tags |
The list grows as new families are registered; the repository’s file is the current
version. IDs are written as in the list (one, 0x3379CFE2, uses capitals
there).
Sources
- uf2families.json – Microsoft’s list of family IDs, read in November 2026 (80 entries)
- USB Flashing Format (UF2) – the README’s rules for family IDs