For engineers and software architects
Online Whiteboard for System Design Diagrams
A system design diagram has two jobs that pull against each other: it has to be drawable while the argument is still happening, and readable by somebody who joins the project a month later. Stencil palettes make the first job slow, and pure freehand makes the second job impossible.
What you need for system design diagrams
Boxes and arrows you can draw as fast as you talk. A design conversation moves faster than a shape palette. If placing a service takes three clicks and a menu, you stop sketching and start operating the tool.
A board that stays quick once the diagram is real. System diagrams grow. A canvas that starts stuttering a few hundred elements in pushes you into splitting one design across four files.
Walk the team through the design, not just show it. A design review is a route through the diagram: entry point, queue, store, then the failure path. A wall of shapes shown all at once is not a review.
A record of how the design changed. The decisions are the artifact, not the drawing. Three weeks later the useful question is what the diagram looked like before somebody moved the queue.
Get the diagram out, and get an outside reviewer in. The diagram's real home is the design doc, and the people who need to read it may not have an account on anything you use.
How Drawdy handles it
Boxes and arrows you can draw as fast as you talk
Draw the rectangle freehand and hold still for a beat: the stroke is read as a shape and comes back clean, without costing you the original stroke. Lasso selection catches a whole cluster with a scribbled loop, so pulling three services apart to make room is one gesture.
A board that stays quick once the diagram is real
Elements are indexed spatially, so selection, erase and hit-testing do not degrade as the board fills, history and redraw diff by reference equality, and live cursors are throttled. A single board holds up to 10,000 elements.
Walk the team through the design, not just show it
Presentation mode runs as an extension on the canvas and steps through the board in order, on the free tier. The reviewers see one part of the design at a time instead of hunting for where you are pointing.
A record of how the design changed
Version history is included on the free tier, and it stores what changed rather than snapshots of the whole board, so stepping back through the design is cheap even on a full canvas.
Get the diagram out, and get an outside reviewer in
Export to PNG or SVG for the doc, or to open .drawdy JSON to keep the editable source. A share link needs no account on the other end, carries either the editor or the viewer role, and is end-to-end encrypted: the board is encrypted in the browser with AES-GCM and the key travels in the URL fragment, which never reaches the server.
When Drawdy is the wrong tool
Some of the work around system design diagrams belongs in another tool. Here is which parts, and where they go.
You are drawing formal UML, entity-relationship models, or network and rack layouts, and you need the stencils that go with them.
Use draw.io.
You want a canvas inside your own product rather than a whiteboard beside it. Drawdy ships no SDK for embedding.
Use tldraw.
You need to open a saved .excalidraw file. Drawdy accepts elements pasted straight out of Excalidraw as editable objects, but it cannot open the file yet.
Use Excalidraw.
FAQ
Questions people ask
Can I use Drawdy for a system design interview?+
Yes. It opens in a browser tab with no install and no account needed to start, so you can be drawing within seconds of the question. Send the interviewer a share link and they can follow along as a viewer, or draw with you as an editor, without signing up for anything.
Does Drawdy have AWS or cloud provider icons?+
No. Drawdy ships no vendor icon libraries, so cloud services are shapes you draw or elements you paste onto the board. If your diagrams depend on official icon sets and technical stencils, draw.io is the better tool for that work.
Can I export the diagram into Confluence or a design doc?+
Export the board to PNG or SVG and drop the file into the doc. There is no Confluence app and no live embed, so the image is the handoff; the open .drawdy JSON export is what keeps the editable source alongside it.
How big can a system diagram get?+
A single board holds up to 10,000 elements. Elements are indexed spatially, so selection, erase and hit-testing stay quick as the diagram fills up rather than slowing down with it.
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