In this note, we outline current practices, tools, and workflows for viser development. We assume that the repository is cloned to ~/viser.

Python install#

We recommend an editable install for Python development, ideally in a virtual environment (eg via conda).

# Install package.
cd ~/viser
pip install -e .

# Install example dependencies.
pip install -e .[examples]

After installation, any of the example scripts (~/viser/examples) should be runnable. A few of them require downloading assets, which can be done via the scripts in ~/viser/examples/assets.

Linting, formatting, type-checking.

First, install developer tools:

# Using pip.
pip install -e .[dev]
pre-commit install

It would be hard to write unit tests for viser. We rely on static typing for robustness. To check your code, you can run the following:

# runs linting, formatting, and type-checking

Message updates#

The viser frontend and backend communicate via a shared set of message definitions:

  • On the server, these are defined as Python dataclasses in ~/viser/src/viser/

  • On the client, these are defined as TypeScript interfaces in ~/viser/src/viser/client/src/WebsocketMessages.tsx.

Note that there is a 1:1 correspondence between the dataclasses message types and the TypeScript ones.

The TypeScript definitions should not be manually modified. Instead, changes should be made in Python and synchronized via the script:

cd ~/viser

Client development#

For client development, we can start by launching a relevant Python script. The examples are a good place to start:

cd ~/viser/examples

When a viser script is launched, two URLs will be printed:

  • An HTTP URL, like http://localhost:8080, which can be used to open a pre-built version of the React frontend.

  • A websocket URL, like ws://localhost:8080, which client applications can connect to.

If changes to the client source files are detected on startup, viser will re-build the client automatically. This is okay for quick changes, but for faster iteration we can also launch a development version of the frontend, which will reflect changes we make to the client source files (~/viser/src/viser/client/src) without a full build. This requires a few more steps.

Installing dependencies.

  1. Install nodejs.

  2. Install yarn.

  3. Install dependencies.

    cd ~/viser/src/viser/client
    yarn install

Launching client.

To launch the client, we can run:

cd ~/viser/src/viser/client
yarn start

from the viser/src/viser/client directory. After opening the client in a web browser, the websocket server address typically needs to be updated in the “Server” tab.


We use prettier. This can be run via one of:

  • prettier -w .

  • npx prettier -w .

from ~/viser/src/viser/client.