On excalidraw.com, the collaboration username is stored in localStorage and there's no URL parameter to pre-set it.

From the source (excalidraw-app/collab/Collab.tsx):

username: importUsernameFromLocalStorage() || "",

If no username is saved, a random one is generated via @excalidraw/random-username.

For the hosted excalidraw.com app: There's no supported way to embed the username in the URL. You'd have to pre-set it in each user's localStorage (excalidraw-collab-username key) before they open the link — which isn't practical for shared links.

If you're self-hosting with the @excalidraw/excalidraw React component: You have full control. You can set collaborator names programmatically via the API:

const collaborators = new Map();
collaborators.set("user-socket-id", {
  username: "Assigned Name Here",
});
excalidrawAPI.updateScene({ collaborators });

And you can call collabAPI.setUsername("Name") to set the local user's name before joining a room.

So the answer depends on your setup:

• excalidraw.com → not possible via URL
• Self-hosted React component → fully configurable via setUsername() / updateScene()