When I was reviewing some site stats last week, I was surprised to note that one of the most popular posts on this site is from February 2010 called Co-Authoring in Excel 2010: Not Supported (Use the Excel Web App Instead). A lot has happened since February 2010 with Excel (and Microsoft), including Office 365 (released June 2011).

So what’s the current story with co-authoring in Excel?

March 2017
Microsoft announced that co-authoring was coming to the Excel desktop client, starting with users of Excel for Windows for Office 365 on the early release schedule (the “Office Insiders Fast” ring of releases):

We’re taking a significant step in completing the co-authoring story across Word, Excel and PowerPoint. Today, we’re enabling co-authoring in Excel on Windows desktops for Office Insiders Fast. This allows you to know who else is working with you in a spreadsheet, see where they’re working and view changes automatically within seconds. We’ll continue using feedback from Insiders to improve the experience before making it available more broadly. Co-authoring is already available in Excel Online, Excel on Android, Windows Mobile and iOS (for Office Insiders). We’re also working on co-authoring in Excel for the Mac—stay tuned for more!

The Excel file must be stored in a supported cloud service: SharePoint Online, OneDrive or OneDrive for Business.

July 2017
Roll forward a few months, and co-authoring in Excel on Windows desktops was released to Office Insiders Slow – in the 1707 (“201707”) release of Excel.

August 2017
Co-authoring in Excel was released with general availability to all Office 365 subscribers. This is valid for Excel for Windows, but not yet for co-authoring in Excel for Mac (although this was promised in March, so it is apparently still coming).