What is Linwood Butterfly?

Linwood Butterfly is a free, open-source note-taking and drawing app built around an infinite canvas. It is designed for visual thinkers who want to handwrite, sketch, annotate, and organize ideas without being confined to a fixed page size. You can use it on Android, Windows, macOS, Linux, or in a browser, with an iOS preview also available. If your work involves stylus input, PDF markup, diagrams, or mixed media documents, Butterfly is built for that kind of task.

What you can do on the canvas

Butterfly treats the page as endless, so a single document can hold many kinds of content side by side:

• Handwrite and sketch with a stylus, touch, or mouse.
• Annotate PDFs and mark up documents directly.
• Sketch interfaces, build diagrams, or plan projects in the same file.
• Mix formats — import camera photos, gallery images, PDFs, and SVGs, then combine them with your own notes.

Because everything stays on one canvas, you do not have to split related material across separate apps or files.

Editing and control over your marks

Butterfly is built so that your first attempt does not have to be your final one.

• Stroke tuning: adjust stroke width, color, smoothing, and texture.
• Edit instead of restart: if a mark is not quite right, you can edit it rather than erase and redraw.
• Everything stays editable: move, resize, recolor, and reorganize elements after placing them.

This matters for tasks like refining a diagram or cleaning up lecture notes after class, where you want to fix details without rebuilding the whole page.

Tools beyond the pen

The app goes past a basic pen-and-eraser setup. Available tools include labels, shapes, polygons, rulers, grids, textures, stamps, a laser pointer, and presentation tools. For recurring work, you can:

• Turn favorite layouts into templates that bundle backgrounds, tools, layers, areas, and pages.
• Save reusable content in packs — stamps, palettes, and styles — so new documents start with what you already use.

If you frequently produce the same kind of document, templates and packs reduce setup time on each new project.

Platforms and how your work is stored

Butterfly runs across desktop, mobile, and the web:

Storage and ownership work as follows:

• Local by default: documents live on your device, and you can keep working without an internet connection.
• Bring your own cloud: you can connect WebDAV services such as Nextcloud to sync, back up, and edit notes across devices.
• Open formats: documents are kept in the documented .bfly and .tbfly formats.
• Open source: Butterfly is free and open source under the GNU AGPL-3.0 license.

There is also experimental collaboration with end-to-end encrypted sessions, either through Swamp or a WebSocket server you host yourself.

Who it fits, and who should look elsewhere

Butterfly is a good fit if you:

• Take notes or sketch with a stylus and want an infinite canvas.
• Need to annotate PDFs or combine images, SVGs, and handwriting in one document.
• Prefer local-first storage and the option to sync through your own WebDAV service.
• Want an open-source tool with documented file formats.

It may be less suitable if you mainly need plain text notes with no drawing, or if you require a mature, fully released iOS app rather than a preview. To evaluate it for your own workflow, the most direct step is to try the web app or download it for your platform and test one real task — for example, importing a PDF and annotating it — before committing your notes to it.