Hackpad

 Hackpad  is an interactive collaborative document editing silo that was acquired by Dropbox and is shutting down on 2017-07-19 (archived). Existing users were encouraged in a 2017-04-21 email to try using Dropbox Paper instead, with the options of importing Hackpad pads into Paper, or exporting your pads into a single zip folder, or do nothing and let pads be automatically migrated to Paper on 2017-07-19, or opt out of automatic migration.