OnlyOffice - Free Online Office Suite

The free (for personal use) service lets you work on your MS Office or LibreOffice documents, spreadsheets, and presentations, online.

OnlyOffice Personal is an online editor that packs the necessary tools to create Microsoft compatible documents, spreadsheets, and presentations, and collaboratively work in real time.

You can also connect your Google Drive, Dropbox, OneDrive, and Yandex.Disk accounts to the service.

It is also possible to selfhost OnlyOffice on your own server.

OnlyOffice

OnlyOffice on Github