butterfly.linwood.dev

Yes. Linwood Butterfly is free and open source software, released under the GNU AGPL-3.0 license. You can download it and use it without paying, and because the source code is open, you can inspect, modify, and redistribute it under the terms of that license. The project also keeps your documents in documented .bfly and .tbfly formats rather than a closed, proprietary container.

That combination matters if you care about lock-in: the license covers the software, and the documented file formats cover your work.

What "free and open source" means here

Two separate things are usually bundled into that phrase, and Butterfly satisfies both:

• Free as in cost — the site presents Butterfly as free and open source, with no pricing signals, subscription tiers, or payment links on the page. There is nothing to buy to use the app.
• Free as in freedom — the GNU AGPL-3.0 license is a strong copyleft license. It guarantees you the right to run, study, share, and modify the software. If you distribute a modified version, the AGPL requires you to release your source under the same license, including when the software is offered over a network.

The AGPL is stricter than permissive licenses like MIT. If you plan to build Butterfly into a hosted product, read the license terms first — the network-use clause is the part that catches people off guard.

Your files stay in open, documented formats

Butterfly stores documents in .bfly and .tbfly formats, and these are documented rather than secret. Practically, that means:

• Your notes and drawings are not trapped in a format only one company can read.
• You can back up, move, or archive files yourself.
• If the project ever stalled, the format is documented well enough for other tools to work with it.

This is the file-format half of "your work belongs to you." The license is the software half.

Local-first by default

Butterfly keeps documents on your device unless you choose to save them elsewhere, and it works without an internet connection. That design reinforces the ownership point: nothing forces your work onto someone else's server.

If you do want sync, you connect your own cloud rather than a mandatory account. The site specifically mentions WebDAV services like Nextcloud for syncing, backing up, and editing notes across devices. That is a bring-your-own-storage model, not a vendor-hosted one.

Where it runs

Butterfly runs on Android, Windows, macOS, Linux, and in the browser, with an iOS preview also available. The same free, open-source app covers all of these, so choosing it does not lock you to one operating system.

What to check before you commit

• License fit — if you only use Butterfly for personal notes and sketches, AGPL-3.0 is a non-issue. If you want to embed or host it commercially, review the AGPL obligations.
• Sync setup — syncing is not automatic out of the box; you bring a WebDAV service such as Nextcloud. If you do not already have one, factor that in.
• Collaboration is experimental — end-to-end encrypted sessions work through Swamp or a WebSocket server you host yourself, and the site labels this experimental. Do not rely on it for critical shared work yet.

For most people asking whether Butterfly is free and open source, the answer is straightforward: yes on both counts, with documented file formats and local-first storage as the practical payoff.

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.

Linwood Butterfly is a free, open-source workspace for handwriting, sketching, annotating, and organizing ideas on an infinite canvas. You can use it if you want notes, PDF markup, diagrams, and images to live in one editable document instead of being split across page-bound apps. It runs on Android, Windows, macOS, Linux, and in the browser, with an iOS preview also available, so the same canvas can move from a desk to a class or meeting.

Core things you can do

The site describes Butterfly as "a workspace for visual thinkers" and lists several concrete uses that can be mixed in the same document:

• Capture lecture notes with a stylus
• Mark up a PDF
• Sketch an interface
• Build a diagram
• Plan a project

Because the canvas is infinite, these tasks are not forced into separate pages. You can keep a lecture note, a PDF annotation, and a diagram side by side and still treat them as one document.

Draw and edit with control

Butterfly supports drawing with a stylus, touch, or mouse. You can adjust stroke width, color, smoothing, and texture. If a mark is not quite right, the site says you can edit it instead of starting over.

Every element stays editable after you place it. You can move, resize, recolor, and reorganize content, so a first attempt does not have to be final. This matters for tasks like sketching an interface or building a diagram, where you often need to shift labels, resize shapes, or change colors after the initial layout.

Bring different media into one document

You can import camera photos, gallery images, PDFs, and SVGs, then combine them with your own notes. The site says you can export clean results in common formats. A practical example: import a PDF handout, annotate it with a stylus, add a photo of a whiteboard, and sketch a diagram next to it, all in the same file.

Use tools beyond pen and eraser

Butterfly includes labels, shapes, polygons, rulers, grids, textures, stamps, a laser pointer, presentation tools, and more. These are useful when a task needs structure rather than freehand drawing:

• Use rulers and grids for precise diagrams or interface sketches
• Use shapes and polygons for flowcharts or system diagrams
• Use labels to annotate parts of a sketch
• Use stamps and textures to reuse visual elements
• Use the laser pointer and presentation tools when walking through your canvas

Reuse layouts and content

You can start with a template that brings together backgrounds, tools, layers, areas, and pages. Favorite layouts can become templates, and frequently used content can become packs, stamps, palettes, and styles available across documents. This is helpful if you repeatedly create the same kind of document, such as a weekly project plan or a standard annotation layout.

Keep control of your files

Butterfly is local by default: you can keep working without an internet connection, and documents live on your device unless you choose to save them elsewhere. You can connect WebDAV services like Nextcloud to sync, back up, and edit notes anywhere. Documents use the documented .bfly and .tbfly formats. The software is free and open source under the GNU AGPL-3.0 license. Experimental collaboration supports end-to-end encrypted sessions through Swamp or a WebSocket server you host yourself.

Where to start

If you want to try it, the site offers a download and a web app, plus documentation and a blog. A reasonable first step is to open the web app or install it on your platform, create a document, and test one of the listed tasks, such as importing a PDF and annotating it, to see whether the infinite canvas and editing model fit your workflow.

Linwood Butterfly runs on Android, Windows, macOS, Linux, and in your browser, with an iOS preview also available. That means you can pick a native app for your main device and still open the same kind of canvas in a browser elsewhere, rather than being locked to one operating system.

Platform options at a glance

Choosing between the download and the web app

The site presents two entry points: Download Butterfly and Try the web app. Both lead to the same canvas concept, so the choice is mostly about your situation:

• Use the downloadable app when you want a persistent install on Android, Windows, macOS, or Linux — for example, a device you carry to class or meetings and use regularly.
• Use the web app when you are on a machine where you cannot or do not want to install software, or when you just want to try Butterfly before committing to a download.

If your device is an iPhone or iPad, the iOS option is a preview, so treat it as an early look rather than a finished platform.

What stays consistent across platforms

Butterfly is built around an infinite canvas for handwriting, sketching, annotating, and organizing, and the site describes it as running "everywhere" — from your desk to your next class or meeting. Several features matter when you move between devices:

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

Practical way to decide

1. Identify the device you will actually draw on most — a tablet with a stylus, a laptop, or a desktop.
2. If that device is Android, Windows, macOS, or Linux, start with the downloadable app.
3. If you need to work on a machine you do not control, open the web app instead.
4. If you are on iOS, check the preview and expect it to be less complete than the other platforms.
5. If you want your notes available in more than one place, set up a WebDAV service like Nextcloud rather than relying on a single device.

The main limitation to keep in mind is that the site does not describe feature parity between the native apps, the web app, and the iOS preview, so if a specific tool matters to you, confirm it on the platform you plan to use.

Yes. Linwood Butterfly is local by default: your documents live on your device and keep working without an internet connection. Syncing is optional and self-directed — you connect your own WebDAV service, such as Nextcloud, to sync, back up, and edit notes across devices. There is no built-in cloud account mentioned in the site's description, so offline use is the baseline and sync is something you bring yourself.

Offline by default

According to the site, Butterfly is designed so you can "keep working without an internet connection," and documents stay on your device "unless you choose to save them somewhere else." That means:

• You can write, sketch, annotate, and organize on the infinite canvas with no connection.
• Your files are not uploaded anywhere by default.
• Nothing about offline use requires a login or an account.

This matters if you take notes in a lecture hall, on a plane, or anywhere with unreliable Wi-Fi — the canvas keeps working and your work stays put.

How syncing works: bring your own cloud

Butterfly does not appear to ship its own sync service. Instead, the site says you can "Connect WebDAV services like Nextcloud to sync, back up, and edit your notes anywhere."

In practice, that means the sync path looks like this:

1. You already have (or set up) a WebDAV-capable service, such as a Nextcloud instance.
2. You connect Butterfly to that service.
3. Your documents sync through your own storage, so you control where the data lives.

The trade-off is explicit: you get full ownership and no vendor lock-in, but you are responsible for having and maintaining the WebDAV server. If you do not already run one, that is the main setup cost.

File formats keep your work portable

Butterfly keeps documents in its documented .bfly and .tbfly formats. Because the formats are documented and the software is open source under the GNU AGPL-3.0 license, your notes are not trapped in a closed system — you can keep, move, and manage the files yourself, which pairs naturally with storing them on your own WebDAV server.

Collaboration is separate and experimental

If you want to work with others rather than just sync your own devices, the site describes experimental collaboration with end-to-end encrypted sessions, run either through Swamp or a WebSocket server you host yourself. Treat this as a distinct, experimental feature rather than a standard sync option — it is for live shared sessions, not for routine backup.

Which setup fits you

The short version: offline is the default and always available; cross-device sync is opt-in through your own WebDAV storage, so plan for that server if you want your notes on more than one machine.