What is co-authoring exactly means?
Co-Authoring is an amazing feature in SharePoint - Office Web Apps which allows multiple users to edit and collaborate concurrently in real time. Yes, You heard it right! Multiple authors can edit one document (Word, Excel, PowerPoint, etc) and simultaneously other user's changes will be reflecting to everyone! Its definitely a great productivity boosting feature.
Multiple users can work on a same document at the same time while they see each other works in the document, so they don't make any conflicts as they make edits. There is no limit in number of users. Any number of people can work on the same document at the same time.
How to use Co-Authoring in SharePoint 2013 with Office Web Apps:Here is how the Co-authoring works in Excel documents with SharePoint 2013 - Office Web Apps:
Step 1: Navigate to any document library/folder where your Excel files are stored. Click on the context menu button and click on More options as in the below screen.
Step 2: Choose “Edit in Browser” menu item from the context menu.
Step 3: This launches your Excel Sheet in Edit mode in the browser. You can get the changes as soon as it’s made by any other user - concurrently editing the document.
When more than one person are working on the same file, You'll get all author's name at the bottom right section.
Alternatively, You can just click on the document to launch it in read-only mode in the browser and then click on "Edit in Browser" command from the ribbon.
Please note, Co-Authoring feature is not available through on all office clients (E.g. Co-authoring is available only through Excel Web Apps for Excel spreadsheets. For word documents, Co-Authoring is available via Microsoft Office Word Application). Also, It doesn't work when you enable check-in/check out functionality! Refer this technet link for supported clients: Overview of co-authoring in SharePoint 2013
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