Documentation

Diagramium is a diagram editor for anyone 18 or older — a teacher building a water-cycle lesson or a team mapping a launch. This guide covers the essentials, then tips tuned to how much you already know. Use the index on the left to jump around.

Start in 30 seconds

1. Pick a type. Open the Diagrams menu (or press Start creating on the home page) and choose one of the twenty-five types.
2. Add content. Drag a shape from the left panel onto the canvas, or type in the Text editor tab.
3. Show it. Press Present to play it back step by step, then Export as PNG, SVG, GIF or video.

Nothing you do is permanent and nothing is uploaded — experiment freely, then clear the canvas and start again.

Three ways to build

• Drag on the canvas — the visual way. Drag shapes from the left panel, then drag from a shape's blue connection dot to another shape to join them. Double-click any shape to rename it.
• Type in the text editor — the fast way. For sequence diagrams, a line like Alice->Bob: Hello draws itself. Canvas and text stay in sync, so you can switch mid-diagram.
• Start from a template — the easy way. Explore has ready-made, editable examples for every type; open one and change the words.

Most people mix all three: start from a template, drag a few shapes, then tidy up the wording in text.

The diagram types

There are twenty-five types, and they all share the same canvas, Present mode and export tools — so learning one teaches you the rest. A quick way to choose:

• Order or timing matters → Sequence or Timeline.
• Steps and decisions → Flowchart, Decision tree or Swimlane.
• Structure and relationships → Org chart, Mind map or Architecture.
• Systems and security → State machine, Data flow, Network or Threat model.

See the full list of diagram types for a one-line description of each, or read which diagram for which job.

Writing diagrams as text

Every diagram has a plain-text form you can type instead of draw — fast for keyboard users, and easy to keep in version control. Sequence diagrams have the richest syntax:

User->WebApp: Sign in (email, password)
WebApp->Auth: Verify credentials
Auth-->WebApp: Token
WebApp-->User: Welcome back

A solid arrow -> is a call; a dashed arrow --> is a reply. Anything after the colon is the message label. The canvas updates as you type, and dragging on the canvas writes the text back — they are two views of one diagram. Export → Text gives you the whole thing to paste elsewhere.

Tuned to your skill level

Present mode

Press Present to reveal a diagram one step at a time — great for teaching, standups and demos. You can add per-step Notes for narration, turn on a progress bar, and go full screen. Step with ← / →, play with Space, and exit any time with Esc.

Present isn't just for showing — it's the source of the animated GIF and video exports below, so a diagram can narrate itself long after you've closed the tab.

Exporting & saving

• Images: PNG or SVG for slides and docs. SVG stays crisp at any size.
• Motion: GIF or video of the Present playback — drop it into chat, a deck, or social.
• Editable: Export → Project (.json) keeps a file you (or a teammate) can reopen and edit.
• Portable: Export → Text gives the plain-text form you can paste anywhere.

Saving & autosave

Your work saves automatically to your browser's local storage as you go — reopen the tab and it's still there. Because that storage lives on your device, two things follow: clearing your browser's site data erases it, and it won't appear on a different device or browser. For anything you want to keep or move, use Export → Project (.json) and reopen the file later, or Export → Text for a copy you can store anywhere.

Keyboard shortcuts

The Text editor tab is a complete keyboard-only path — everything the canvas can do, you can also type. See the accessibility statement.

Privacy & data

Everything that matters runs in your browser: your diagrams live on your device and in the files you export, and no feature uploads them. An account is optional and free (it syncs your favourites and likes, and unlocks the animated GIF, video and animated SVG exports — there is no paid tier). We do not track you — the only thing recorded is an anonymous count of how often each ready-made diagram is opened or played. See the privacy policy.

FAQ

Who can use it? Adults only: Diagramium requires you to be at least 18 years old — for every feature, with or without an account. See the Terms of Use.

Is it free? Yes — free, with no account.

Does it work offline? Once the page has loaded, yes — it runs entirely in your browser.

Where are my diagrams? In your browser's local storage on this device, plus any files you export. Diagrams are never uploaded.

Can I collaborate? Share an exported Project (.json) or the Text form — a teammate reopens it and keeps editing.

Still stuck? Browse the diagram types, read the blog, or just open the editor and experiment.