Open UF2 files in your browser
The firmware you drag onto a Raspberry Pi Pico or an Adafruit board. See what a UF2 holds right here, before you flash it. Nothing leaves your device.
Or drop it anywhere on this page
What you'll see
Your firmware opens as the program it holds, the chip it's for and where it writes in flash.
- The chip it's for • RP2040, RP2350, ESP32, nRF and more
- The program • Its name, version and build date, when it says
- Where it writes • Each region and its size
- Save the flash image as a .bin
About UF2
Microsoft made UF2 in 2017 for MakeCode, so a board could show up as a USB drive and take new firmware by drag and drop. The Raspberry Pi Pico, Adafruit boards with CircuitPython and many keyboards and 3D printer boards flash this way, and MicroPython, CircuitPython and QMK ship .uf2 files.
A UF2 is made of 512 byte blocks, each with 256 bytes to write and the address to write them at, plus a family ID naming the chip it's for, so a board can turn down firmware for another chip.
Filepeek names the chip from the family ID, and reads the program's name, version and build date where the Pico SDK or ESP-IDF write them. It shows where the firmware writes in flash and how much, says when blocks are missing, and saves the flash image as a .bin.
USB Flashing Format
.uf2
Format
- MIME type
- application/octet-stream
- Made by
- Microsoft, for MakeCode
- Released
- 2017
Inside the file
- Blocks
- 512 bytes, 256 to write
- Each names
- Its address and its chip
- Flashed by
- Copying it to the board
- Made by
- Microsoft, for MakeCode
Opens in every browser
Browsers download UF2 files. Filepeek reads them in Chrome, Edge, Firefox and Safari.
- YouChromeOpens through Filepeek
- YouEdgeOpens through Filepeek
- YouFirefoxOpens through Filepeek
- YouSafariOpens through Filepeek
Apps that open UF2
- WindowsCopy it to the board's drive in File Explorer
- MacCopy it to the board's drive in Finder
- iPhone and iPadNo app opens it
- AndroidNo app opens it
Questions
How do I flash a UF2 file?
Put the board in its bootloader, like holding BOOTSEL on a Raspberry Pi Pico as you plug it in, or pressing reset twice on many Adafruit boards. It shows up as a drive, and you copy the .uf2 onto it.
Why does nothing happen after I copy the UF2?
A board takes only firmware for its own chip and quietly ignores the rest. Filepeek names the chip a UF2 is for, so you can tell before you flash it.
Which Pico is this UF2 for?
Filepeek names the chip from the family ID in each block: RP2040 for the Pico and Pico W, RP2350 for the Pico 2 and Pico 2 W.
Can I turn a UF2 into a .bin?
Yes. Filepeek saves the flash image as a .bin, every byte from the first address on, with gaps filled as erased flash.