> ## Documentation Index
> Fetch the complete documentation index at: https://wb-21fd5541-workspaces-notebooks.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Configure a notebook

Configure a notebook's settings to control its appearance, runtime behavior, and editor preferences.

## Open notebook settings

Notebook settings apply only to the current notebook. You can configure display and export options, add custom CSS and HTML, and change other notebook-specific behavior.

To open notebook settings:

1. In the upper-right corner of the notebook, select **Notebook Settings** (<Icon icon="gear" iconType="solid" />).
2. In the settings menu, change the settings as needed.

To learn more, see marimo's [Notebook settings](https://docs.marimo.io/guides/configuration).

## Configure runtime behavior

Runtime settings control how the notebook responds when it starts, when a cell changes, and when an imported Python module changes.

### Understand execution modes

The runtime supports two execution modes: autorun and lazy.

#### Autorun mode

In autorun mode, the notebook automatically runs dependent cells when any of the following events occur:

* You run or edit a cell.
* You interact with a UI element.
* An imported Python module changes while module autoreloading is enabled.

#### Lazy mode

In lazy mode, running a cell marks its downstream cells as stale instead of running them automatically.

When you run a cell that has stale upstream cells, the notebook runs the upstream cells first. This process ensures that the cell receives up-to-date inputs.

### Change runtime settings

To change the runtime settings:

1. In the notebook footer, select the notebook runtime button (<Icon icon="bolt-lightning" iconType="solid" />).
2. Configure the applicable settings:

| Setting               | Behavior                                                    | Options                           |
| --------------------- | ----------------------------------------------------------- | --------------------------------- |
| **On startup**        | Whether the notebook runs automatically when it starts      | **Autorun** or **Lazy**           |
| **On cell changes**   | Whether dependent cells run automatically after a cell runs | **Autorun** or **Lazy**           |
| **On module changes** | Whether affected cells run when an imported module changes  | **Off**, **Autorun**, or **Lazy** |

To learn more, see marimo's [Runtime configuration](https://docs.marimo.io/guides/configuration/runtime_configuration/).

## Configure editor preferences

To configure editor preferences:

1. In the upper-right corner of the notebook, select **NOTEBOOK SETTINGS** (<Icon icon="gear" iconType="solid" />).
2. In the settings menu, select **Editor**.
3. Configure preferences such as code font size, line numbers, and syntax highlighting.

To learn more, see marimo's [Editor features](https://docs.marimo.io/guides/editor_features/overview/).