Cascade
Map together, in the same chart, at the same time
Collab mapping normally runs on file swaps: someone exports a
.osz, someone else opens it, edits, sends it back, and
whoever forgot to pull first loses their work. Cascade keeps everyone in
one live chart instead, so a guest difficulty or a full collab set is
just two people in the same editor.
Invite by osu! username
Save a map to your account, open Share, and invite someone by their osu! username. They get a notification in their Cascade inbox and the map appears in their My Maps. Nobody has to send a file or agree on who is holding the latest version.
Editor or viewer
Each person you invite is an editor, who can change the chart, or a viewer, who can follow along and comment but not edit. Viewer access is the honest way to show a work in progress to someone whose opinion you want without risking the file.
You can see each other work
Everyone in the session shows up with their avatar, their cursor and their playhead, so you can watch where the other person is working and stay out of each other's way. Notes appear as they are placed. There is no save button to coordinate around and no merge step at the end.
Comments pinned to a timestamp
Feedback on a chart is useless if nobody can find the bar it is about. Comments in Cascade are anchored to a time in the song and to a difficulty, so clicking one jumps the editor straight to the pattern being discussed. Threads can be resolved once the note has been dealt with.
Collaboration needs an account, because invitations are tied to osu! usernames. Local maps stay entirely on your machine.