> For the complete documentation index, see [llms.txt](https://docs.n8n.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.n8n.io/build/work-with-data/reference-data/use-the-ui-mapper.md).

# Use the UI mapper

Data mapping means referencing data from previous nodes. It doesn't include changing (transforming) data, just referencing it.

When you need data from a particular node in your workflow, you can [reference nodes by name](/build/work-with-data/reference-data/reference-previous-nodes.md). This is useful when your workflow has multiple branches or when you need to access data from several steps back.

You can map data in the following ways:

* Using the expressions editor.
* By dragging and dropping data from the **INPUT** pane into node parameters. This generates the expression for you.

![Creating expressions in the UI](/files/ka34oQo4czLSfjmcTHXk)

For information on errors with mapping and linking items, refer to [Item linking errors](/build/work-with-data/reference-data/link-data-items/item-linking-errors.md).

See [Common ways of referencing](/build/work-with-data/reference-data/reference-previous-nodes.md#common-ways-of-referencing).