---
title: Dual preview and synced scrolling
nav: Dual preview
order: 4
description: Two documents side by side: load a reference file, authorize a base folder, scroll both panes proportionally, and switch to reading mode.
updated: 2026-08-12
---

## Why two previews

Translating, checking a spec, rewriting an old version into a new one — all of those mean
*reading A while writing B*. Browser tabs can't sit side by side, and lining up two windows by hand gets old fast.
So the editor carries a second preview.

## Opening it

The **Side-by-side dual preview** button splits the preview area in half:

- **The left half** always follows the file you are editing, live.
- **The right half** is independent: it shows whatever you load into it, untouched by your typing.

The right half has two buttons:

| Button | What it does |
| --- | --- |
| **📂 Load MD** | pick any `.md` to display on the right |
| **📁 Authorize folder** | set a base folder so the right half can show full relative paths instead of bare file names |

You can also **drop a file onto the right half** and it lands there; drop it on the left half and it becomes
the file you are editing. Whichever side of the midline your cursor is on is where the file goes.

## Synced scrolling

Above the right half there is a **Sync scroll** checkbox. With it on, both sides move **proportionally**:
scroll one pane to 40 % and the other goes to its own 40 %.

It deliberately does not try to align line by line. Two documents almost never share line counts or
paragraph heights, so forcing that would make the panes jump around while you scroll. Proportional
scrolling is the more predictable behaviour.

Uncheck it and each side scrolls on its own again.

## Reading mode

Turn off **Show / hide editor** and only the previews remain. Combined with dual preview, that is two
documents side by side with no editing field taking up space. Turn it back on and your text and scroll
position are still there.

The sidebar can be collapsed too, for the widest possible reading area. Both toggles are remembered in
your browser, so the next visit looks the way you left it.

## Closing it

Press **Side-by-side dual preview** again (or the close button on the right half) to return to a single
preview. Whatever you loaded on the right never affects the file you are editing — it is read-only reference
material from beginning to end.