# Binder: Sources

> The rail on the left.

Glider documentation · Data · Web page: https://cgglider.com/docs/binder/sources/

Sections of this page: [How binding works](https://cgglider.com/docs/binder.md) · [Sources](https://cgglider.com/docs/binder/sources.md) · [Live feeds](https://cgglider.com/docs/binder/feeds.md) · [Sheets](https://cgglider.com/docs/binder/sheets.md) · [Action binding](https://cgglider.com/docs/binder/actions.md) · [Troubleshooting](https://cgglider.com/docs/binder/troubleshooting.md)

| Source | Detail shown | Empty state |
| --- | --- | --- |
| Page data | Key count | “This page has no data yet. Add keys in the Data tab's JSON view.” |
| Live feeds | Mapped-field count per poller; disabled pollers dimmed | “No API pollers yet. Add one in Units to bind fields straight to a feed.” |
| Sheets | Bound-cell count per sheet | “No sheets yet. Upload one in Logic → Sheets to bind fields to cells.” |

Whichever source is selected, the right pane is the same key tree with the same click-to-connect behaviour. If the feed or sheet you were browsing is deleted while the tab is open, the Binder falls back to Page data rather than rendering an empty pane.

![The source rail with feeds and sheets.](https://cgglider.com/docs-shots/binder-sources.png)