CoderPad Drawing Mode: The Whiteboard for System Design

CoderPad's whiteboard is called Drawing Mode. It is an Excalidraw canvas that opens inside a live CoderPad Interview pad, is shared with everyone in the pad, and survives being closed and reopened. As of September 9, 2026, CoderPad documents it for live interviews only; nothing in the documentation places it in CoderPad Screen tests or in the free sandbox. Its final state is saved into the interview playback. If a system design or architecture round is on your schedule, this is the tool you will draw in, and this article covers how it behaves and how to get ready for it.

How Drawing Mode works

CoderPad's Drawing Mode documentation describes it as "powered by Excalidraw," the open-source hand-drawn-style whiteboard. Either participant opens it with the "Drawing Mode button located in the top left hand corner" of the pad.

The canvas is shared but the window is not. "The drawing window contents are always synced between ALL pad users, but each pad user controls whether or not their drawing window itself is open or closed at any moment." The interviewer can be watching your diagram while you think they are looking at your code, and the reverse.

Closing it loses nothing. "The contents of all participants will still be accessible upon re-opening." The tools are the Excalidraw set: shapes, arrows, text, and image import, so an interviewer can drop an existing architecture diagram onto the canvas and ask you to change it.

What happens to the drawing afterward

The board is part of the record. "You will be able to see the final state of the drawing as part of the pad playback for review," and a Drawing tab appears in playback whenever the mode was used. The playback documentation also lists time spent in drawing sections in the pad summary. Note the word final. CoderPad documents the end state of the whiteboard, not a stroke-by-stroke replay of it, which is the opposite of the code editor, where every keystroke is kept. The full inventory is in whether CoderPad records your screen.

How interviewers use it

CoderPad's own guidance for architecture interviews describes two patterns. In one, the interviewer gives requirements and watches you design from a blank canvas. In the other, they upload a diagram of an existing system, describe a problem such as a scaling or redundancy failure, and ask you to modify the design and explain the tradeoffs. The second pattern is harder to rehearse, because the starting diagram is theirs.

Both patterns are usually paired with the code pane. It is common to sketch the components, then be asked to write the interface or a critical function for one of them in the editor, so expect to move between the whiteboard and the code in the same session.

How to prepare

CoderPad's documentation recommends that interviewers give candidates advance notice of Drawing Mode "to familiarize themselves with the tool beforehand." Whether or not yours does, three things are worth doing.

Learn Excalidraw itself. The canvas is the open-source tool, and excalidraw.com runs the same interface. Spend fifteen minutes on boxes, arrows, labels, and grouping so the tool disappears on the day. The sandbox is not documented as including Drawing Mode, so this is the substitute; what the sandbox does cover is in how to practice in the CoderPad sandbox.

Practice narrating while drawing. A shared whiteboard means the interviewer sees each box as it lands. Silence while you draw reads as uncertainty. Name each component as you place it and say what it is for.

Have a design routine. Requirements, scale estimates, a first simple diagram, the bottleneck, the fix, the tradeoff. A repeatable structure keeps a live whiteboard from turning into a pile of boxes. One such structure is in how to answer system design questions step by step.

Drawing Mode and AI

If the interviewer has enabled AI Assist in the pad, it is a text panel beside the editor, and its prompts and outputs are saved in playback. It does not draw. Using it for design during a live round means asking it questions in view of the interviewer, which is the only mode CoderPad documents. Whether an AI assistant belongs in a design interview at all, and how to use one when it is allowed, is covered in how to use an AI assistant in a system design interview.

What this means for candidates

Expect the whiteboard to be shared, persistent, and kept. Draw as if the interviewer is watching, because they can be. Learn Excalidraw before the interview, narrate as you go, and bring a structure to the problem. The format of the rest of the session, from question types to a test-day checklist, is in the CoderPad interview format and preparation guide.