If the Digispark Pro bootloader becomes corrupted (generally only a concern on Beta units), or you want to replace it with another bootloader, upload code directly (to avoid the bootloader taking up space), or download the existing code to a computer - then you can use AVR-ISP to do so.

You will need the hex file to upload and a current version of AVRDUDE that can talk to the Attiny167 (the main chip on the Digispark Pro).

Windows - everything you need is here, just unzip to a folder: avrdude.zip

OS X: Grab and install the AVR Crosspack (or another AVRDude copy) http://www.obdev.at/products/crosspack/index.html and then put the following avrdude.conf (unzip first) in the same folder as AVRDude, replacing the existing one: avrdude_conf.zip

Linux: Grab a recent version of AVRDude (from package manager, or binary, or build it) and then put the following avrdude.conf (unzip first) in the same folder as AVRDude, replacing the existing one: avrdude_conf.zip

Connect your Pro to an Uno with the Arduino ISP sketch loaded (Examples→ArduinoISP) or connect it to an AVRISP programmer.

If connecting to an Uno follow the diagram below. For an ISP programmer connect MOSI to MOSI, MISO to MISO, SCK to SCK, RST to RST, VCC to VCC (should be 5v) and GND to GND. Look at the bottom of the Digispark Pro for the pin names or this pin out chart: http://digispark.s3.amazonaws.com/DigisparkProDiagram2.png

Open a command prompt/shell in the folder that contains AVRDude - and use the following command:

avrdude -p attiny167 -c arduino -P [COM PORT OF YOUR ARDUINO] -U:flash:w:ProBootloaderR2.hex