Frequently Asked Questions

Contact us at info@msofficeaddin.com or via the /contact page. We are a Microsoft Partner Center verified publisher with 250+ Office Add-in projects delivered over 5+ years. Project quotes are returned within 24 business hours.

Office Add-ins use HTML, CSS, and JavaScript via the Office.js API. They run cross-platform on Windows, macOS, and Outlook on the Web with no local installation required. COM Add-ins are legacy .NET/Windows-only extensions requiring administrator rights and do not run on Mac or Web. Microsoft has deprecated COM add-in development in favour of Office.js.

It depends on scope. A simple task pane add-in costs far less than an enterprise build with Microsoft Graph, SSO, and CRM integration. We work to your budget and send a fixed-price estimate within 24 business hours of a free discovery call, so there are no surprises later.

Yes. As a Microsoft Partner we handle the full AppSource submission, including manifest setup, validation requirements, and Partner Center configuration. If Microsoft flags anything during certification, we fix it and resubmit until your add-in is approved.

We build custom add-ins for Excel, Word, Outlook, PowerPoint, and Teams, plus SharePoint SPFx solutions. Every add-in is built on Office.js, so it runs across Windows, Mac, and the web from a single codebase.

Yes. We migrate legacy VSTO and COM add-ins to the modern Office.js platform so they run cross-platform on Windows, Mac, and the web. We map your existing features, rebuild them with current APIs, and keep the workflow your team already knows.

We follow the Office.js Mailbox requirement set model (currently Mailbox 1.10 for Microsoft 365). A typical Outlook add-in takes 4–10 weeks: 1 week discovery, 1–2 weeks design, 3–6 weeks build, 1 week AppSource submission (3–7 business day Microsoft review). We handle Azure AD SSO via MSAL OBO flow, manifest configuration, and AppSource certification.

Simple task-pane add-ins (read/write data, basic UI): 2–4 weeks. Add-ins requiring Microsoft Graph API, SSO, or CRM integration: 6–10 weeks. Complex enterprise solutions with multi-tenant Azure infrastructure: 10–16 weeks. All timelines include AppSource submission and post-launch support.

All add-ins we build support Microsoft 365 (Current, Monthly Enterprise, and Semi-Annual channels), Office 2021, and Office 2019. Support for Office 2016 depends on the specific Office.js requirement sets used and is confirmed per project. Add-ins do not support Office 2013 or earlier.

Enterprise deployment uses Centralized Deployment via the Microsoft 365 Admin Center, where admins push the add-in to all users or specific groups with no end-user installation required. Public distribution uses Microsoft AppSource. SharePoint App Catalog is the third option for SharePoint-specific add-ins. All three methods use the same Office Add-in manifest file.