Add-ins for every Office host
Task panes and ribbon commands for Word, Excel, Outlook, and PowerPoint — often sharing one Office.js codebase across hosts.
Microsoft Office
Office Plugin Development
Office add-in development creates web-based task panes, ribbon commands, and document or workbook tools for supported Word, Excel, Outlook, and PowerPoint clients. It is intended for organizations replacing manual Office workflows or assessing whether a legacy VSTO or COM plugin can move to Office.js, subject to the APIs available in each host.
What I build
What is included in Office add-in development?
PowerPoint add-in development
Slide generation, brand-template automation, and content insertion so decks come out on-brand without manual formatting.
Supported multi-platform delivery
One add-in that runs on Office for Windows, Mac, iPad, and the web, with graceful checks where a host's API differs.
VSTO / COM migration
Migrating compatible parts of legacy Windows-only plugins to Office.js so they can target additional supported clients and reduce reliance on per-machine installation.
Problems this solves
What problems can Office add-in development solve?
- A legacy VSTO/COM plugin that breaks on Office updates and doesn't run on Mac or the web.
- Repetitive Office tasks — formatting decks, assembling documents — done by hand daily.
- PowerPoint decks that drift off-brand because there's no automation enforcing templates.
- Needing the same tool available in more than one Office app.
Example use cases
What does Office add-in development look like in practice?
Branded deck builder
A PowerPoint add-in that turns a short form into a fully branded slide deck using approved templates and layouts.
Clause inserter for Word
A Word add-in that drops approved, formatted clauses into contracts from a central library.
Shared tool across hosts
A single add-in running in both Word and Excel, sharing logic while adapting its UI to each host.
Tech stack
What technologies power Office add-in development?
Core
- Office.js
- TypeScript
- React
Tooling
- Yeoman generator
- Unified app manifest
Hosts
- Word
- Excel
- Outlook
- PowerPoint
Delivery
- Azure Static Web Apps
- AppSource
- Sideloading
Process
How does Office add-in development work?
01
Pick hosts & scope
Decide which Office apps and what the add-in does in each.
02
Build with Office.js
Task panes/commands with shared, typed code.
03
Test supported clients
Verify required features on the agreed Windows, Mac, and web host versions.
04
Publish
AppSource or internal deployment with a clean manifest.
This is the overview page. For the two hosts I'm asked for most, see Outlook plugin development and Excel add-in development. It's all part of my broader Microsoft 365 development work.
Related services
Outlook Plugin Development
Outlook add-in development creates tools that operate in supported reading, compose, and event-based Outlook contexts using Office.js and, where required, Microsoft Graph. It is intended for organizations that need email or calendar workflows, CRM context, validation, or internal actions available from Outlook, with features limited by the client and Mailbox requirement set.
Excel Add-in Developer
Excel add-in development creates custom functions, task panes, worksheet automation, and API-connected data workflows using Office.js. It is intended for organizations that need calculations, reporting, imports, or two-way data synchronization inside supported Excel clients, with availability determined by platform and requirement set.
Microsoft 365 Developer
Microsoft 365 development creates add-ins and integrations for supported Outlook, Word, Excel, and PowerPoint clients using Office.js, Microsoft Graph, and Entra ID. It is intended for organizations that need to place business workflows inside Microsoft 365 or connect Microsoft data to another system, with compatibility determined by each host and requirement set.
FAQ
Questions, answered
- What's the difference between an 'Office plugin' and an 'Office add-in'?
- 'Plugin' commonly refers to a Windows-only VSTO/COM add-in. Office.js add-ins can target supported Office clients on Windows, Mac, iPad, and the web, although available APIs vary by host and version.
- Do you build PowerPoint add-ins?
- Yes — as a PowerPoint add-in developer I build slide generation, template automation, and content insertion so decks stay on-brand automatically.
- Will the add-in run on Mac and Office on the web?
- Yes. Office.js add-ins are cross-platform; I add capability checks where a specific host or platform exposes different APIs.
- Can you migrate our old VSTO or COM plugin?
- I assess and migrate the parts of a legacy Windows-only plugin supported by Office.js. Cross-client parity depends on the APIs available in each target host and version.
- Are you an experienced Office.js developer?
- Yes — Office.js is core to my work across Outlook, Word, Excel, and PowerPoint, including manifests, permissions, and AppSource submission.
Let's build it together
Email me with what you need — I'll reply with a clear plan and next steps. Prefer chat? WhatsApp works too.