# Citation hover preview

Hover a citation, footnote marker or figure reference and a popup shows what it points to: the bibliography entry, the footnote or the figure. You read it without leaving the page you're on.

**Available in version 3.7 or later.**

**Most often you hover a `[12]` citation to see the reference behind it.** At a glance:

- **Preview:** hover a link to another place in the document; the popup shows the target
- **Plain-text citations:** `[12]` references that aren't links are previewed too
- **Scroll the popup:** `Shift + wheel` with the cursor on the link, or the wheel with the cursor on the popup
- **Zoom the popup:** `Ctrl + wheel`, on the link or on the popup
- **Turn it on / off:** `Toggle Citation Hover Preview` in the [Command Palette](Command-Palette.md), or `CitationHoverDelay`

![Citation hover preview: hovering citation 2 shows its entry from the References page](https://files.sumatrapdfreader.org/assets/sumatrapdf/docs/img/citation-hover-preview-2d6d.png)

## Turn the preview on or off

The preview is off by default. To turn it on or off:

- [Command Palette](Command-Palette.md): `Ctrl + K`, then `Toggle Citation Hover Preview` (`CmdToggleHoverPreview`). On sets a 300 ms delay.
- [Advanced settings](Advanced-options-settings.md): `CitationHoverDelay` is how long, in milliseconds, you hover before the popup shows. `-1` turns the preview off.

```
CitationHoverDelay = 300
```

## Preview a citation

Hover the link and wait for the popup. It shows the region around the target: a whole bibliography entry, a footnote, an equation or a figure.

- Move the cursor away and the popup closes.
- Click the link to jump to the target as usual; `Alt + Left` comes back.
- Web links inside the popup can be clicked.

## Read more of the target with the mouse wheel

**With the cursor on the link:**

- `Shift + wheel` scrolls the popup. It continues onto the previous or next page.
- `Ctrl + wheel` zooms the popup.
- The plain wheel scrolls the document, as if the popup weren't there.

**With the cursor on the popup** (it stays open while you move onto it):

- The wheel scrolls the popup.
- `Ctrl + wheel` zooms it.

Note: some mouse software (Logitech Options+, Microsoft Mouse and Keyboard Center) sends `Shift + wheel` as horizontal scrolling. That scrolls the popup too.

## Tips

- Use `Shift + wheel` to read a long reference entry without moving the mouse.
- Move onto the popup when you want to read more of it: the plain wheel works there.
- Lower `CitationHoverDelay` (e.g. `150`) if the popup feels slow, raise it if it gets in the way.
- Use `Toggle Citation Hover Preview` to switch it off for a document with many links.

## See also

- [Hyperlinks](Hyperlinks.md) — following links and coming back
- [Scrolling, zooming, navigating](Scrolling-and-zooming.md) — the wheel in the document
- [Advanced settings](Advanced-options-settings.md) — `CitationHoverDelay`