micromamba is a small, pure-C++ executable with enough functionalities to bootstrap fully functional conda-environments.

Still at early stage, it’s main usage is in continous integration pipelines: since it’s a single executable, it reduces dramatically bandwidth usage and provide fast operations.


micromamba supports a subset of all mamba or conda commands and implements a command line interface from scratch.
You can see all implemented commands with micromamba --help:
$ micromamba --help

  shell                       Generate shell init scripts
  create                      Create new environment
  install                     Install packages in active environment
  update                      Update packages in active environment
  repoquery                   Find and analyze packages in active environment or channels
  remove                      Remove packages from active environment
  list                        List packages in active environment
  package                     Extract a package or bundle files into an archive
  clean                       Clean package cache
  config                      Configuration of micromamba
  info                        Information about micromamba
  constructor                 Commands to support using micromamba in constructor
  env                         List environments
  activate                    Activate an environment
  run                         Run an executable in an environment
  ps                          Show, inspect or kill running processes
  auth                        Login or logout of a given host
  search                      Find packages in active environment or channels

To activate an environment just call micromamba activate /path/to/env or, when it’s a named environment in your root prefix, then you can also use micromamba activate myenv.

micromamba expects to find the root prefix set by $MAMBA_ROOT_PREFIX environment variable. You can also provide it using CLI option -r,--root-prefix.

Named environments then live in $MAMBA_ROOT_PREFIX/envs/.

For more details, please read about configuration.

After activation, you can run install to add new packages to the environment.

$ micromamba install xtensor -c conda-forge

Using create, you can also create environments:

$ micromamba create -n xtensor_env xtensor xsimd -c conda-forge
          __  ______ ___  ____ _____ ___  / /_  ____ _
         / / / / __ `__ \/ __ `/ __ `__ \/ __ \/ __ `/
        / /_/ / / / / / / /_/ / / / / / / /_/ / /_/ /
       / .___/_/ /_/ /_/\__,_/_/ /_/ /_/_.___/\__,_/

conda-forge/noarch       [====================] (00m:01s) Done
conda-forge/linux-64     [====================] (00m:04s) Done


  Prefix: /home/wolfv/miniconda3/envs/xtensor_env

  Updating specs:

  - xtensor
  - xsimd

  Package        Version  Build        Channel                    Size

  _libgcc_mutex      0.1  conda_forge  conda-forge/linux-64     Cached
  _openmp_mutex      4.5  1_gnu        conda-forge/linux-64     Cached
  libgcc-ng        9.3.0  h5dbcf3e_17  conda-forge/linux-64     Cached
  libgomp          9.3.0  h5dbcf3e_17  conda-forge/linux-64     Cached
  libstdcxx-ng     9.3.0  h2ae2ef3_17  conda-forge/linux-64     Cached
  xsimd            7.4.9  hc9558a2_0   conda-forge/linux-64     102 KB
  xtensor         0.21.9  h0efe328_0   conda-forge/linux-64     183 KB
  xtl             0.6.21  h0efe328_0   conda-forge/linux-64     Cached


  Install: 8 packages

  Total download: 285 KB


Confirm changes: [Y/n] ...

After the installation is finished, the environment can be activated with:

$ micromamba activate xtensor_env

Specification files#

The create syntax also allows you to use specification or environment files (also called spec files) to easily re-create environments.

The three supported syntaxes are: yaml, txt and explicit spec files.

Simple text spec files#

The txt file contains one spec per line. For example, this could look like:

numpy 1.19
xsimd >=7.4

To use this file, pass:

$ micromamba create -n from_file -f spec_file.txt -c conda-forge


You can pass multiple text spec files by repeating the -f,--file argument.

YAML spec files#

More powerful are YAML files like the following, because they already contain a desired environment name and the channels to use:

name: testenv
  - conda-forge
  - python >=3.6,<3.7
  - ipykernel >=5.1
  - ipywidgets

They are used the same way as text files:

$ micromamba create -f env.yml


CLI options will keep precedence over target prefix or channels specified in spec files.


YAML spec files do not allow multiple files.

Explicit spec files#

Using conda you can generate explicit environment lock files. For this, create an environment and execute:

$ conda list --explicit --md5

These environment files look like the following and precisely “pin” the desired package + version + build string:

# This file may be used to create an environment using:
# $ conda create --name <env> --file <this file>
# platform: linux-64

To install such a file with micromamba, just pass the -f flag again:

$ micromamba create -n xtensor -c conda-forge -f explicit_env.txt