:bulb: Hint: Using emulator as described here is useful during firmware development. If you intend to use the emulator without modifying the firmware, you might be looking for Trezor User Env.

Emulator is a unix version of Core firmware that runs on your computer.


There is neither boardloader nor bootloader and no firmware uploads. Emulator runs the current code as is it is and if you want to run some specific firmware version you need to use git for that (simply checkout the right branch/tag). Actually, maybe we should call it simulator to be precise, because it does not emulate the device in its completeness, it just runs the firmware on your host.

Emulator significantly speeds up development and has several features to help you along the way.

⚠️ Disclaimer ⚠️

This emulator is for development purposes only. It uses a pseudo random number generator, and thus no guarantee on its entropy is made. No security or hardening efforts are made here. It is, and will continue to be, intended for development purposes only. Security and hardening efforts are only made available on physical Trezor hardware.

Any other usage of the emulator is discouraged. Doing so runs the risk of losing funds.

How to run

  1. build the emulator
  2. run emu.py inside the poetry environment:
    • either enter poetry shell first, and then use ./emu.py
    • or always use poetry run ./emu.py
  3. start the bridge:
    • to initialise the bridge with emulator support, start it with trezord-go -e 21324
    • alternatively, launch the desktop suite from the command line with the argument --bridge-dev

Now you can use the emulator the same way as you use the device, for example you can use Trezor Suite, use our Python CLI tool (trezorctl), etc. Simply click to emulate screen touches.


Run ./emu.py --help to see all supported command line options and shortcuts. The sections below only list long option names and most notable features.

Debug and production mode

By default the emulator runs in debug mode. Debuglink is available (on port 21325 by default), exceptions and log output goes to console. To indicate debug mode, there is a red square in the upper right corner of Trezor screen.


To enable production mode, run ./emu.py --production, or set environment variable PYOPT=1.

Initialize with mnemonic words

In debug mode, the emulator can be pre-configured with a mnemonic phrase.

To use a specific mnemonic phrase:

./emu.py --mnemonic "such deposit very security much theme..."

When using Shamir shares, repeat the --mnemonic option:

./emu.py --mnemonic "your first share" --mnemonic "your second share" ...

To use the "all all all" seed defined in SLIP-14:

./emu.py --slip0014
./emu.py -s

Storage and Profiles

Internal Trezor's storage is emulated and stored in the /var/tmp/trezor.flash file by default. Deleting this file is similar to calling wipe device. You can also find /var/tmp/trezor.sdcard for SD card. Starting the emulator with -e / --erase will delete the files beforehand.

You can specify a different location for the storage and log files via the -p / --profile option:

./emu.py -p foobar

This will create a profile directory in your home ~/.trezoremu/foobar containing emulator run files. Alternatively you can set a full path like so:

./emu.py -p /var/tmp/foobar

You can also set a full profile path to TREZOR_PROFILE_DIR environment variable.

Specifying -t / --temporary-profile will start the emulator in a clean temporary profile that will be erased when the emulator stops. This is useful, e.g., for tests.


By default, emulator output goes to stdout. When silenced with --quiet, it is redirected to ${TREZOR_PROFILE_DIR}/trezor.log. You can specify an alternate output file with --output.

Running subcommands with the emulator

In scripts, it is often necessary to start the emulator, run a command while it is available, and then stop it. The following command runs the device test suite using the emulator:

./emu.py --command pytest ../tests/device_tests

Profiling support

Run ./emu.py --profiling, or set environment variable TREZOR_PROFILING=1, to run the emulator with a profiling wrapper that generates statistics of executed lines.

Memory statistics

Run ./emu.py --log-memory, or set environment variable TREZOR_LOG_MEMORY=1, to dump memory usage information after each workflow task is finished.

Run in gdb

Running ./emu.py --debugger runs emulator inside gdb/lldb.

Watch for file changes

Running ./emu.py --watch watches for file changes and reloads the emulator if any occur. Note that this does not do rebuild, i.e. this works for MicroPython code (which is interpreted) but if you make C changes, you need to rebuild yourself.

Press p on your keyboard to capture emulator's screen. You will find a png screenshot in the src directory.

Disable animation

Run ./emu.py --disable-animation, or set environment variable TREZOR_DISABLE_ANIMATION=1 to disable all animations.