Once a release is cut, napari is distributed in two main ways:

  • Packages: both to PyPI and conda-forge.

  • Installers: bundles that include napari plus its runtime dependencies in a step-by-step executable.


Despite its numerous dependencies, napari itself is a simple Python project that can be packaged in a straight-forward way.

Creating and submitting the packages to PyPI (the repository you query when you do pip install) is handled in the .github/workflows/make_release.yml workflow. Creation is handled with make dist (as specified in our Makefile) and submission is done using the official PyPA GitHub Action. This workflow will also create a GitHub Release.

Once the Python package makes it to PyPI, it will be picked by the conda-forge bots, which will automatically submit a PR to the napari-feedstock repository. This is all automated by the conda-forge infrastructure (see previous examples), so we only need to check that the metadata in the recipe has been adjusted for the new release. Pay special attention to the runtime dependencies and version strings!

Once the conda-forge CI is passing and the PR is approved and merged, the final packages will be built on the default branch and uploaded to the conda-forge channel. Due to the staging steps and CDN synchronization delays, the conda packages can take up to 2h to be available.

Nightly packages

We also build nightly packages off main and publish them to the napari/label/nightly channel. These are the same packages that are used in the constructor installers (see below), so their CI is specified in .github/workflows/

To do it in a conda-forge compatible way, we actually clone napari-feedstock and patch the source instructions so the code is retrieved from the repository branch directly. The version is also patched to match the setuptools-scm string. After rerendering the feedstock, we run conda-build in the same way conda-forge would do and upload the resulting tarballs to our channel.

Additionally, the tarballs are also passed as artifacts to the next stage in the pipeline: building the constructor installers (more below).


Once the packages have been built and uploaded to their corresponding repositories, we can bundle them along with their dependencies in a single executable that end users can run to install napari on their systems, with no prior knowledge of pip, conda, virtual environments or anything.

A software installer is usually expected to fulfill these requirements:

  • It will install the application so it can be run immediately after.

  • It will provide a convenient way of opening the application, like a shortcut or a menu entry.

  • It will allow the user to uninstall the application, leaving no artifacts behind.

Right now, we are using two ways of generating the installers:

  • With briefcase, which takes PyPI packages.

  • With constructor, which takes conda packages.

conda packages offer several advantages when it comes to bundling dependencies, since it makes very little assumptions about the underlying system installation. As a result, constructor bundles include libraries that might be missing in the target system and hence should provide a more robust user experience.

Briefcase-based installers

briefcase based installers are marked for deprecation so we will not discuss them here. If you are curious, you can check and .github/workflows/make_bundle.yml for details.

Constructor-based installers

constructor allows you to build cross-platform installers out of conda packages. It supports the following installer types:

  • On Linux, a shell-based installer is generated. Users can execute it with bash

  • On macOS, you can generate both PKG and shell-based installers. PKG files are graphical installers native to macOS, and that’s the method we use with napari.

  • On Windows, a graphical installer based on NSIS is generated.

The configuration is done through a construct.yaml file, documented here. We generate one on the fly in the script. Roughly, we will build this configuration file:

# os-agnostic configuration
name: napari
version: 0.4.12  # depending on workflow triggers, this can also be a dev snapshot for nightlies
company: Napari
license: <points to a generated license that bundles the licenses of all dependencies>
  # - local  # only in certain situations, like nightly installers where we build napari locally
  - napari/label/bundle_tools  # temporary location of our forks of the constructor stack
  - conda-forge
  - napari
  - napari-menu  # provides the shortcut configuration for napari
  - python 3.7  # pinned to the version of the running interpreter, configured in the CI
  - conda  # we add these to assist in the plugin installations
  - mamba  # we add these to assist in the plugin installations
  - pip    # we add these to assist in the plugin installations
  - napari-menu  # don't create shortcuts for anything else in the environment

# linux-specific config
default_prefix: $HOME/napari-0.4.12  # default installation path

# macos-specific config
name: napari-0.4.12  # override this because it's the only way to encode the version in the default
                     # installation path
installer_type: pkg  # otherwise, defaults to sh (Linux-like)
welcome_image: resources/napari_1227x600.png  # bg image with the napari logo on bottom-left corner
welcome_file: resources/osx_pkg_welcome.rtf  # rendered text in the first screen
conclusion_text: ""  # set to an empty string to revert constructor customizations back to system's
readme_text: ""  # set to an empty string to revert constructor customizations back to system's
signing_identity_name: "Apple Developer ID: ..."  # Name of our installer signing certicate

# windows-specific config
welcome_image: resources/napari_164x314.png  # logo image for the first screen
header_image:  resources/napari_150x57.png  # logo image (top left) for the rest of the installer
icon_image: napari/resources/icon.ico  # favicon for the taskbar and title bar
default_prefix: '%USERPROFILE%/napari-0.4.12'  # default location for user installs
default_prefix_domain_user: '%LOCALAPPDATA%/napari-0.4.12'  # default location for network installs
default_prefix_all_users: '%ALLUSERSPROFILE%/napari-0.4.12'  # default location for admin installs
signing_certificate: certificate.pfx  # path to signing certificate

On the OS-agnostic keys, the main keys are:

  • channels: where the packages will be downloaded from. We mainly rely on conda-forge for this, where napari is published. However, we also have napari/label/bundle_tools, where we store our constructor stack forks (more on this later). In nightly installers, we locally build our own development packages for conda without resorting to conda-forge. To make use of those (which are eventually published to napari/label/nightly), we unpack the GitHub Actions artifact in a specific location that constructor recognizes as a local channel once indexed.

  • specs: the conda packages that should be provided by the installer. Constructor will perform a conda solve here to retrieve the needed dependencies.

  • menu_packages: restrict which packages can create shortcuts. We only want the shortcuts provided by napari-menu, and not any that could come from the (many) dependencies of napari.

Then, depending on the operating systems and the installer format, we customize the configuration a bit more.

Default installation path

This depends on each OS. Our general strategy is to put it under napari-<version> in the user directory. However, there are several constrains we need to take into account to make this happen:

  • On Windows, users can choose between an “Only me” and “All users” installation. This changes what we understand by “user directory”. This is further complicated by the existence of “domain users”, which are not guaranteed to have a user directory per se.

  • On macOS, the PKG installer does not offer a lot of flexibility for this configuration, so we need to override the name to include the version tag.


Graphical installers can be customized with logos and icons. These images are stored under the resources/ directory (outside of the source), with the exception of the square logos/icons (which are stored under napari/resources/ so the shortcuts can find them after the installation).

Some of the steps are also configured to display a custom text, like the license or the welcome screen on macOS.

Note: Most of the branding for macOS is only available in our fork. This has been sent upstream but it’s not accepted or released yet.


In order to avoid security warnings on the target platform, we need to sign the generated installer.

On macOS, once Apple’s Installer Certificate has been installed to a keychain and unlocked for its use, you can have constructor handle the signing via productsign automatically. However, this is not enough for a warning-free installation, since its contents need to be notarized and stapled too. For this reason, constructor has been modified to also codesign the bundled _conda.exe (the binary provided by conda-standalone, see below) with the Application Certificate. Otherwise, notarization fails. After that, two actions take care of notarizing and stapling the resulting PKG.

On Windows, any Microsoft-blessed certificate will do. Our constructor fork allows us to specify a path to a PFX certificate and then have the Windows SDK signtool add the signature. Note that signtool is not installed by default on Windows (but it is on GitHub Actions).

Details of our constructor stack fork

Many of the features here listed were not available on constructor when we started working on it. We have added them to the relevant parts of the stack as needed, but that has resulted in a lot of moving pieces being juggled to make this work. Let’s begin by enumerating the stack components:

  1. constructor is the command-line tool that builds the installer. It depends on conda to solve the specs request. It also requires a copy of conda-standalone (a PyInstaller-frozen version of conda) to be present at build time so it can be bundled in the installer. This is needed because that conda-standalone copy will handle the extraction, linking and shortcut creation when the user runs the installer on their machine.

  2. conda-standalone is a frozen version of conda. Among its dependencies, we can find menuinst, which handles the creation of shortcuts and menu entries.

  3. menuinst was only used on Windows before our work, so we basically rewrote it to handle cross-platform shortcuts.

  4. conda interfaces with menuinst to delegate the shortcut creation. Since this was only enabled on Windows, we needed to unlock the other platforms and rewrite the parts that assumed Windows only behaviour. Surprise, this involved custom solver behaviour too!

Since menuinst is frozen together with conda for conda-standalone, every little change in any of those requires a rebuild of conda-standalone so constructor can find the new version during the installer creation. As a result, we needed to fork and repackage all four components!

Notice the repackaging needs. It’s not enough to fork and patch the code. We also need to create the conda packages and put them in a channel so the downstream dependencies can pick them when they are rebuilt. This repackaging is done through a separate conda-forge clone that only handles our forks. It is configured to use GitHub Actions (instead of Azure) and upload to the napari channel (instead of conda-forge).

For example, if a patch is introduced in menuinst, the following needs to happen before it makes it to the final napari installer:

  1. Write and test the patch. Make sure it passes its own CI.

  2. Make sure conda still works with the new changes. It needs to call menuinst after all.

  3. Create the menuinst package and upload it to

  4. Rebuild and upload conda-standalone so it picks the new menuinst version.

  5. Trigger the napari CI to build the new installer.

Very fun! So where do all these packages live?





jaimergp/constructor @ menuinst+branding




conda-forge/conda-standalone-feedstock PR#21


jaimergp/conda @ cep-menuinst



jaimergp/menuinst @ cep


Most of the forks live in jaimergp’s account, under a non-default branch. They are published through the jaimergp-forge every time a commit to master is made. Versions are arbitrary here, but they are set to be greater than the latest official version, and the build number is incremented for every rebuild.

The only exception is conda-standalone. It doesn’t have its own repository or fork because it’s basically a repackaged conda with some patches. Those patches live in the feedstock only. The other difference is that the feedstock does not live in jaimergp-forge, but just as draft PR in the conda-forge original feedstock. This is because, for some reason, if conda-standalone is built on GitHub Actions machines, the Windows version will fail with _ssl errors which do not appear in Azure. For this reason, the CI is run as normal on conda-forge, and then the artifacts are retrieved from the Azure UI and manually uploaded to the napari channel. Fun again!

Eventually all these complexities will be gone because all of our changes will have been merged upstream. For now, this not the case. Speaking of which, what are our changes? Below you can find a high-level list of the main changes introduced in the stack.

Changes in menuinst
  • Add cross-platform specification for shortcut configuration

  • Enable support on Windows, Linux and macOS

  • Re-engineer environment activation

  • Maintain backwards compatibility with Windows

  • Simplify API

  • Remove CLI

Changes in conda
  • Add API support for menuinst v2

  • Enable code paths for non-Windows Platforms

  • Fix shortcut removal logic

  • Add --shortcuts-only flag to support menu_packages constructor key natively

Changes in conda-standalone
  • Unvendor menuinst patches

  • Do not vendor constructor NSIS scripts

  • Adapt conda constructor entry point for the new menuinst API

Changes in constructor
  • Use --shortcuts-only

  • Add branding options for macOS PKG installers

  • Always leave _conda.exe in the install location

  • Do not offer options for conda init or PATH manipulations (these should be Anaconda specific)

  • Add signing for Windows

  • Add notarization for macOS PKG