> ## Documentation Index
> Fetch the complete documentation index at: https://docs.docwriter.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Live preview

> Open a popup window that re-renders whenever your hooks produce a new artifact.

When a hook has an **output** field set (a path to the artifact it
produces, e.g. `main.pdf`, `essay.html`, `diagram.svg`), DocWriter shows a
floating **Preview** button in the top-right of the editor. Clicking it
opens a popup window that displays the artifact and reloads automatically
every time the hook produces a new version.

## How matching works

The preview button appears when the active tab matches a hook's output
path. The matching is conservative. It triggers when:

* The active tab is the source file the hook consumes (e.g. you have
  `main.tex` open and the hook's output is `main.pdf`), or
* The active tab's stem matches the output's stem (you have `essay.md`
  open and the hook's output is `{{stem}}.html`).

If the button does not appear, the most likely cause is the hook's output
field is empty or the active tab does not match any hook's scope. See
[Hooks](/automation/hooks).

## Opening the preview

Click the **Preview** button. A popup window opens, sized 900×1200,
showing the rendered artifact. DocWriter supports four kinds of output:

| Extension                 | Renderer                                   |
| ------------------------- | ------------------------------------------ |
| `.pdf`                    | Bundled PDF.js viewer with synctex support |
| `.html` / `.htm` / `.svg` | Same-origin iframe                         |
| `.png` / `.jpg` / etc.    | `<img>` in a scrolling wrapper             |
| `.txt` / `.md`            | Plain text in an iframe                    |

## Live reload

The preview window subscribes to a server-sent-events bus. Every time
your hook finishes, the preview reloads the file:

* **PDF.** Scroll position, page number, and zoom level are preserved
  across reloads.
* **HTML.** `scrollX` and `scrollY` are preserved.
* **Image.** Wrapper scroll position is preserved.

You do not need to refresh manually. The header shows the timestamp of
the last reload and a connection-status indicator (connected /
disconnected).

## SyncTeX (LaTeX projects)

For PDFs produced by `pdflatex -synctex=1` (the LaTeX template hook
provides this flag), the preview supports two-way navigation between the
PDF and the source:

* **Backward sync.** Double-click any text in the PDF. DocWriter
  resolves the click to the source `.tex` file and line, switches to that
  file in the editor, and scrolls to the line.
* **Forward sync.** In the editor, the menu has a **Show in PDF**
  command. The preview window scrolls to the corresponding page and
  position.

Both directions shell out to the `synctex` binary (part of TeX Live and
MacTeX). If `synctex` is not on your `PATH`, both directions silently
no-op.

## Themes

The preview window picks up the editor's current theme (light, dark,
solarized, etc.) and applies it to the PDF.js viewer chrome. The
document itself is unchanged. Themes only restyle the viewer, not the
rendered PDF or HTML.

## When the preview button is not enough

For workflows that produce non-file outputs (server logs, REPL output,
test results), use the history pane to follow hook output instead. Every
hook run's stdout and stderr is captured there.

## Where to go next

* [Hooks](/automation/hooks). Set up the hook that produces the output.
* [Editing an Overleaf LaTeX project](/guides/overleaf). A complete
  LaTeX preview workflow.