Multiplayer Editing
Multiplayer editing is now in SketchUp Labs on SketchUp for Web at https://labs.sketchup.com/app.
When granting a collaborator access to a model, you can provide them with Edit access. Edit access gives collaborators permission to edit the model you’ve invited them to collaborate on with you. With Multiplayer editing enabled in your model’s Share Settings, all collaborators with Edit access can co-edit together in real-time.

You can set access levels when inviting a collaborator or any time after. For more information on setting access levels, see Sharing a Model.

Controlling Multiplayer Editing
Multiplayer editing is available in SketchUp for Web Labs. Members of the Trimble Connect project containing the model file can enable and disable multiplayer editing at any time.
To enable or disable multiplayer editing, follow these steps:
Click Share. The Sharing modal will open.
Click Share Settings.
Move the Enable multiplayer editing toggle to the on position.
To disable, move the toggle to the off position.Note: With multiplayer editing off, only one editor can work in the file at a time. When a new editor opens it, the current editor is removed.
Click Back.
Click Done to save your settings.
With multiplayer editing on, collaborators with the Edit permission can add, edit, and delete entities in your model. They can use every tool and every import and export option their subscription includes.
All other collaboration functionality remains available to editors. For more information on collaboration features like commenting, following other users, or controlling visibility, see Real Time Viewing.