--- title: "Office Online Server retirement: co-authoring in M-Files" url: "https://ctrldocs.com/blog/office-online-server-retirement/" language: "en" description: "Microsoft retires Office Online Server on 31 December 2026. M-Files customers who co-author through it can move to M-Files Cloud or to OneDrive with CtrlShare." dateModified: "2026-10-14" --- [CtrlShare](https://ctrldocs.com/blog/) # Co-authoring in M‑Files: Office Online Server retires Microsoft retires Office Online Server on 31 December 2026. M‑Files customers who co-author through it can move to M‑Files Cloud, or co-author through OneDrive with CtrlShare. 30 October 2025 Krystian Biały 2 min read ![A Word document checked out for co-authoring with CtrlShare, with its co-authors listed beside a preview of the document](https://ctrldocs.com/img/2t4EGHMkrU-200.webp) In this article 1. [What Office Online Server did](#what-office-online-server-did) 2. [The choice for on-premise M‑Files customers](#the-choice-for-on-premise-m-files-customers) 3. [CtrlShare: co-authoring without OOS](#ctrlshare-co-authoring-without-oos) 4. [Co-authoring on your own terms](#co-authoring-on-your-own-terms) M‑Files checks a document out to one person at a time, so nobody overwrites anyone else’s changes and every version is kept. Most of the time that is the right default. It is the wrong answer when a team has to write in the same document together, which is why [co-authoring](/products/ctrlshare/ "CtrlShare") exists as a separate route. Until now, M‑Files users have had three options for co-authoring: - **Office Online Server (OOS)**: an on-premise server. - **CtrlShare**: co-authoring in Microsoft 365 through OneDrive for Business. - **Native Microsoft 365 co-authoring** in the Business edition of M‑Files, running in M‑Files Cloud. For anyone running M‑Files outside M‑Files Cloud, that has meant a choice of two: CtrlShare or Office Online Server. With Microsoft retiring OOS, that choice is going away, and it is worth settling on a replacement well before OOS reaches end of support. ## What Office Online Server did[#](#what-office-online-server-did) OOS provided browser-based versions of Word, Excel and PowerPoint for on-premise environments. M‑Files integrated with it through WOPI (Web Application Open Platform Interface), which put co-authoring directly in the browser without requiring a full move to the cloud. [Microsoft has scheduled end of support for Office Online Server](https://techcommunity.microsoft.com/blog/officeeos/announcing-the-retirement-for-office-online-server/4462402) on **31 December 2026**. After that date there are no security patches and no updates, which takes it out of the running for enterprise use. Every M‑Files customer that relies on OOS for co-authoring is affected. ## The choice for on-premise M‑Files customers[#](#the-choice-for-on-premise-m-files-customers) If you run M‑Files on-premise, there are two ways forward: 1. **Upgrade to M‑Files Business in M‑Files Cloud**, which has co-authoring built in. 2. **Find an alternative** that keeps co-authoring without forcing a full migration. For plenty of organisations the first option is not practical: compliance requirements, infrastructure already paid for, or a deliberate decision to keep M‑Files under their own control. That is the gap CtrlShare fills. [See what CtrlShare does with a checked-out document](https://ctrldocs.com/products/ctrlshare/), from the vault to OneDrive and back as a new version. ## CtrlShare: co-authoring without OOS[#](#ctrlshare-co-authoring-without-oos) CtrlShare removes the dependency on Office Online Server by using OneDrive for Business and the co-authoring that is already built into Microsoft Office. - **One click.** Check a document out from M‑Files to OneDrive for Business. - **The desktop apps.** Co-author in the full Microsoft Office desktop experience, not only the [more limited web version](https://ctrldocs.com/blog/co-authoring-for-professional-services/). - **Permissions from M‑Files.** Grant read or write rights and revoke access from the vault. - **External people.** Invite them securely, without exposing public links. - **Fewer collisions.** With OneDrive doing the co-authoring, version conflicts and lost changes are less likely. ## Co-authoring on your own terms[#](#co-authoring-on-your-own-terms) With no Office Online Server underneath it and no move to M‑Files Cloud required, M‑Files stays where you decided to run it. If OOS is what your co-authoring runs on today, the date is already set. [Check what CtrlShare needs to run](https://ctrldocs.com/products/ctrlshare/), or [ask for a trial](https://ctrldocs.com/contact/?product_interest=CtrlShare). We answer the same working day. [← All articles](https://ctrldocs.com/blog/) In this article 1. [What Office Online Server did](#what-office-online-server-did) 2. [The choice for on-premise M‑Files customers](#the-choice-for-on-premise-m-files-customers) 3. [CtrlShare: co-authoring without OOS](#ctrlshare-co-authoring-without-oos) 4. [Co-authoring on your own terms](#co-authoring-on-your-own-terms) [Book a demo](https://ctrldocs.com/contact/) ## See the products at work Book a demo and we'll show you the products that fit your M‑Files setup. [Book a demo](https://ctrldocs.com/contact/)