Excalidraw

Excalidraw is the whiteboarding tool you use when you don't want to think about which whiteboarding tool to use. It looks hand-drawn. It loads in two seconds. It's free. The diagrams you make in it feel like the diagrams you'd draw on a real whiteboard, which somehow makes them more readable than the slick vector graphics Miro produces. For founders explaining architecture, mapping flows, or sketching ideas, Excalidraw is the obvious choice. The whole thing is open source. Excalidraw.com is free with no signup. You can self-host it. You can use it offline. Drag a URL with your diagram baked into it (Excalidraw encodes diagrams into URL state so you can share without an account). For a tool that thousands of founders and engineering teams use daily, the 'free, no account, instantly usable' default is rare and good. The paid product (Excalidraw+) is the team-collaboration version. $7/user/month gets you collaborative editing, shared workspaces, exporting to PNG/SVG, and a few quality-of-life features. Most solo founders never need this; the free tool is enough. But for teams that draw diagrams together, Excalidraw+ replaces FigJam or Miro at a fraction of the price. What Excalidraw is genuinely great for: architecture diagrams, system flow charts, simple wireframes, decision trees, anything that involves boxes and arrows with labels. The hand-drawn aesthetic stays charming even when the diagram is complex. Pair it with the AI feature (paid, generates a starter diagram from a prompt) for first-draft scaffolds. What it's not for: production-quality slides (use Pitch or Gamma), wireframes for design handoff (use Figma), serious infinite-canvas brainstorming for 20+ person workshops (Miro or FigJam still win). Excalidraw shines in the 1-5 person diagramming use case. My take: install Excalidraw as a bookmark today if you haven't. It's the kind of tool that becomes part of your workflow within a week — every time you need to explain a system or sketch an idea, you'll reach for it. Pair with the VS Code extension (yes, there's one) to draw diagrams inside your code editor. For solo founders, the free tier is forever. For teams of 5+ doing collaborative architecture work, Excalidraw+ is the cheapest serious whiteboarding tool you can buy.