The best tools for system design interviews in 2026.
Short answer
For remote system design interviews, Excalidraw is the standard whiteboard tool. For onsite interviews, you'll draw on a physical whiteboard. Use BoardSnap to snap the board after the session and get a structured summary you can review, annotate, and use for mock practice — in about ten seconds.
System design interviews test your ability to sketch a scalable architecture under pressure — not your ability to use a diagramming tool. The tool should be invisible.
Onsite interviews: physical whiteboard
The physical whiteboard is what you'll face at most onsite loops. You draw boxes, label them, draw arrows for data flow, note caching layers, write throughput numbers in margins. The board is the interview.
Remote interviews: Excalidraw
Excalidraw has become the de facto standard for remote system design interviews. It's free, browser-based, requires no account, and has a hand-drawn aesthetic that matches the informal tone of a whiteboard session. Most interviewers are comfortable with it. CoderPad also offers a whiteboard mode that some companies use.
Practice and prep: that's where BoardSnap helps
For candidates doing mock system design sessions — with a coach, a study partner, or solo — BoardSnap closes the feedback loop.
- Do the mock session on a physical whiteboard (same conditions as the onsite interview).
- Snap the board when you're done. BoardSnap AI reads the diagram, labels, and margin notes.
- Get a structured summary: components, data flows, tradeoffs noted, decision points. This is your practice artifact.
- Review the AI chat to ask follow-up questions: "What's missing from this design?" "How would this scale to 10x traffic?"
For teams running recurring architecture review sessions (not interviews but real design work), the same workflow applies. Create a project per service or domain; every architecture board from every session lives there.
See the full "Can I use BoardSnap for system design interviews?" page for the end-to-end interview prep workflow.
Frequently asked
Should I practice system design on a whiteboard or in Excalidraw?
Both. Practice in Excalidraw so you're comfortable with the remote interview format, but also do sessions on a physical whiteboard since most onsite loops still use one. BoardSnap works for physical whiteboard practice sessions — snap after each session to build a library of your practice designs.
See it work in ten seconds.
BoardSnap is free on the App Store. Snap a board — get a summary and action plan.