When you look at the Node type, you’ll notice width and height attributes. It might seem like you can just update those. But according to the React Flow docs, those values are read-only. The same goes for measured: { width: number; height: number }.

So how do you actually change a node’s dimensions?

The React Flow team recommends using CSS. From the docs:

“You shouldn’t try to set the width or height of a node directly. It is calculated internally by React Flow and used when rendering the node in the viewport. To control a node’s size you should use the style or className props to apply CSS styles instead.”

That usually works. But there’s a catch.

If you want a consistent way to both set and get a node’s dimensions, relying on the style prop might not be enough. Why? Because of the NodeResizer component.

NodeResizer lets users resize nodes manually using UI handles. But when they do, React Flow doesn't update the style prop. Instead, it directly modifies the width and height attributes using internal state changes.

If you look at how NodeResizer works under the hood, you’ll see that React Flow uses a NodeDimensionChange to update the node’s size.

So how can you trigger that same kind of change programmatically using only official React Flow methods?

Use applyNodeChanges from the React Flow API:

const customDimensionsChange: NodeDimensionChange = {
  id: 'node-1',
  type: 'dimensions',
  dimensions: { width: 300, height: 200 },
  setAttributes: true,
};

setNodes((nodes) => applyNodeChanges([customDimensionsChange], nodes));

This updates the width and height attributes properly. It’s the most consistent way to change node dimensions programatically in React Flow.