Concepts

This page introduces the main ideas behind Folio. Each section points to the guide with the details.

Projects and presentations

A project groups related presentations, such as those for a client, a course or a team. Each project can have its own theme, which applies to all of its presentations.

A presentation is a text. The title shown in the sidebar comes from the @title definition at the start of the text. Without it, the presentation is shown as Untitled.

In the sidebar, use New project to create a project. Hover over a project to create a New presentation, rename it or delete it.

Definitions and slides

The text of a presentation has two parts:

Definitions, at the top, on lines that start with @: title, theme, colors, fonts, styles and components.
Slides, right after. The first piece of content starts slide 1, and each line with --- starts a new slide.

@title 2026 planning
@theme paper

# 2026 planning
Goals, deadlines and owners.

---
# Goals
- Grow the customer base
- Reduce response times

The --- line also accepts attributes that configure the whole slide, such as --- {.dark align=center}. See Layout.

Editor, preview and thumbnails

The editing screen has three parts that work together:

Part	What it does
Editor	Where you write. Errors and warnings are underlined and listed in the bottom panel, with the line and a hint on how to fix them.
Preview	Shows the slide where the cursor is and updates as you type. Click an element to move the cursor to its line.
Thumbnails	Sit below the preview and show every slide, so you can move around the presentation.

An error does not stop the rest of the presentation from showing: Folio draws everything it can and tells you exactly what needs fixing. The full list of codes is in Error messages.

Automatic saving

You never need to save. Folio saves the text shortly after you stop typing, even when it still has errors, so your draft is never lost.

The indicator at the top of the editor shows the current state:

Indicator	Meaning
Saved	Everything you wrote is stored.
Unsaved changes	There are changes waiting to be saved.
Saving…	The text is being sent.
Could not save — retrying	Saving failed, for example with no connection. Folio tries again on its own.
Version conflict	The presentation changed somewhere else. See the next section.

Conflicts between tabs

If the same presentation is open in two tabs or on two devices, one could save over the other. To prevent that, Folio detects when the text changed somewhere else, pauses saving and shows a Version conflict notice with two options:

Use the saved version: discards your changes in this tab and loads the saved text.
Keep mine: saves the text from this tab over the saved version.

Version history

Folio keeps versions of the presentation while you work. Open the panel with the Version history button at the top of the editor to see the versions, browse the slides of each one and restore the one you want.

There are three kinds of version:

Kind	When it is created
Automatic	Periodically, while you edit.
Named	When you name the current version with Save version.
Before restore	Right before a restore, so you can undo it.

See the details in History.

Project theme

The project theme is a text with definitions only (@theme, @color, @font, @style and @component) that applies to every presentation in the project. Open it with the palette icon, Project theme, next to the project name in the sidebar.

Each presentation can override anything from the project theme. See Themes.

Uploaded images

Besides images from the web, you can upload images to the project with the Insert image button, by dragging a file into the editor or by pasting an image. Folio inserts a reference in the text in the form asset: followed by an identifier, which works in any presentation in the project.

Accepted formats and limits are in Images.

Next steps

Writing slides: everything you can write on a slide.
Layout: columns, grids and alignment.
Presenting: full screen, presenter mode and PDF.