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Free with an account · syncs across devices

The whiteboard built for system design interviews.

Drag in load balancers, caches, queues, microservices. Connect them with arrows. Rename a box mid-conversation when the interviewer asks “what about reads?”. Export the picture as a PNG when you’re done - or copy it as Mermaid and paste straight into a PR.

See worked examples
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29
System-Design Shapes
∞
Diagrams Per Account
60
Step Undo History
PNG
Export Format
What the Canvas looks like
Architecture Canvas
Saved
Client
API GW
Load Bal.
Database
Cache
Queue
CDN
Client
API GW
Load Bal.
Service A
Service B
Cache
Postgres
Kafka
Drag from the palette
Auto-saved to your account
Edges drawn with one click
Simple 3-Step Flow

How It Works

01
Sign in, hit Open
Free account, ten seconds. The first time you arrive there's a starter diagram on the canvas so you can poke the controls before you start drawing your own.
02
Drag, connect, rename
Pull a shape from the palette on the left. Drag from a handle on one box to start an arrow to another. Double-click anything to rename it inline. Same muscle memory as Excalidraw or Miro - no manual to read.
03
Auto-saved as you go
No save button. Every change syncs to your account in the background, so the diagram you sketched on your laptop opens on your phone an hour later. Export PNG for docs; copy as Mermaid for PRs.
Why it's actually useful

Built for Interview Pace

Mock SD interviews come at you fast. The whiteboard is sized, shaped, and shortcut-driven to keep up.

Shapes for things you actually draw
Load balancer, API gateway, cache, queue, CDN, microservice, lambda, S3, websocket - plus the classic flowchart set if you'd rather think in process / decision / IO. No generic boxes pretending to be infra.
Connect with one drag
Four handles on every shape. Pull from one to start an arrow. Make it dashed for a fallback, animated for a live stream, or recolour it to mark a hot path. Right-click an edge to switch the arrowhead style.
Follows you across devices
Every edit syncs to your account in the background. Sketched on a laptop, finished on a tablet, glanced at on a phone before the interview. No save button, no losing work because the tab crashed.
60 steps of undo
Try a layout. Hate it. Ctrl+Z back to where you were. The history captures everything - shape moves, edge edits, group changes - so experimenting never costs you the diagram you had.
PNG for docs, Mermaid for PRs
One click saves a PNG of the canvas. Another click copies the diagram as Mermaid flowchart syntax - paste it into a GitHub PR description and the markdown renders the picture for reviewers.
Holds up on a screen share
Nodes stay legible when projected to a Zoom share. Inline label editing means you can rename a box mid-sentence without breaking eye contact. Highlighter and laser pointer for live walk-throughs.
Minimap when it outgrows the screen
Auto-revealed as soon as the diagram exceeds the viewport. Drag the viewport rectangle to fly across - no scroll-wheel guesswork, no zooming out and getting lost.
Paste Mermaid, get an editable diagram
Got a flowchart from ChatGPT or a colleague's doc? Paste the Mermaid code into the Custom tab and the editor parses it, lays it out, and drops the result onto the canvas as shapes you can move and restyle.

Free, with an account.

Sign in once and your diagrams travel with you. No payment details, no trial timer, no “free for the first three diagrams” catch.

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