Expert Solutions

Transforming Office Productivity Through Custom Add-ins

Professional Microsoft Office and Google Workspace development services tailored to automate workflows and boost business efficiency.

Office.js
Office.js
React
React
Vue
Vue
TypeScript
TypeScript
Azure
Azure
Google Script
Google Script
OpenAI
OpenAI
Claude
Claude
Gemini
Gemini
Azure AI
Azure AI
Next.js
Next.js
Angular
Angular
Firebase
Firebase
AWS
AWS
PHP
PHP
Python
Python
C#
C#
Tailwind CSS
Tailwind CSS
n8n
n8n
Stripe
Stripe

Who We Are

MSOfficeAddin.com is a specialized development agency focused on custom Microsoft Office and Google Workspace add-ins. Over the past five years we have shipped 250+ projects for clients worldwide, including businesses in Germany and across Europe.

250+

Projects Delivered

98%

Satisfaction Rate

5+

Years Experience

30+

Countries Served

Why Choose Us

  • Office.js Specialists, 250+ add-ins delivered since 2021
  • Delivery in 2–8 weeks (standard) or 6–12 weeks (Graph-integrated)
  • Azure AD SSO, MSAL OBO flow, Microsoft Graph security on every project
  • Registered AppSource Publisher, avg. 3–7 day certification turnaround
  • 50+ VSTO-to-Office.js migrations completed for enterprise clients

Companies that trust our add-ins

1 Platform
Primmo
EyeMail Inc
Interject
Inflo
MyGatePass
Otisco
Partfiniti
QuikTurn
Tallemu
1 Platform
Primmo
EyeMail Inc
Interject
Inflo
MyGatePass
Otisco
Partfiniti
QuikTurn
Tallemu

What We Do

Microsoft Office Add-ins Development

Microsoft Office Add-ins Development

MSOfficeAddin builds custom Microsoft Office add-ins for Excel, Outlook, Word, PowerPoint, SharePoint, and Teams using Office.js and the Microsoft 365 platform. From CRM-integrated Outlook add-in workflows to financial-automation Excel tools, our certified developers deliver AppSource-ready, cross-platform solutions for enterprise teams across the US, UK, and Australia.

Authentication & Identity

Authentication & Identity

We build the authentication layer for Office add-ins, including Microsoft SSO, OAuth 2.0, Azure AD app registration, and multi-tenant identity. Your users sign in once and the add-in handles everything else.

AppSource Publishing Services

AppSource Publishing Services

We provide end-to-end Microsoft AppSource submission and certification support, from manifest preparation through reviewer communication and resubmission. We publish your Office add-in to the Microsoft marketplace so enterprise IT admins can deploy it across their organization.

Google Workspace Add-ons

Google Workspace Add-ons

Custom Google Workspace add-on development for Sheets, Docs, Gmail, and Drive. Professional Apps Script and REST API solutions for Google Workspace automation.

Our Delivery Process

A structured approach to turning requirements into enterprise solutions.

1

Discovery

Scoping call + workflow analysis. We document Office.js API requirements and define the manifest, permissions, and authentication model before writing a line of code.

2

Design

Fluent UI wireframes and task-pane architecture. We align on API requirement sets (e.g., ExcelApi 1.14, Mailbox 1.10) to ensure cross-version compatibility.

3

Build

Agile sprints using Office.js, React, TypeScript, and Azure. Daily builds are testable via sideloading in your own Microsoft 365 tenant.

4

Deploy

Security audit, manifest validation, and AppSource submission. Microsoft review typically completes in 3–7 business days.

5

Support

Post-launch monitoring and compatibility updates for new Microsoft 365 releases. Response time: 24 business hours.

What Our Clients Say

Join 100+ businesses who trust us with their critical Office automation and enterprise add-in development.

"Amazing work. The Excel plugin was built exactly around what I needed and has made the process much faster and easier to manage. Communication was clear throughout, the turnaround was quick, and the final result worked well without needing constant back and forth. They clearly understood the problem."

C
Chris SimonUnited StatesExcel Add-in Development

"MSOfficeAddin truly exceeded expectations in software development, showcasing impeccable professionalism and profound code expertise. Working with the team was a breeze thanks to excellent cooperation and punctual delivery. HIGHLY recommend their services!"

V
Visup SRLRepeat Client · ItalyOffice Add-in Development

"MSOfficeAddin delivered a flawless software project with incredible attention to detail and professionalism. Working with the team was a breeze as they were consistently responsive and cooperative, all while demonstrating EXCELLENT language fluency. 👍"

V
Visup SRLRepeat Client · ItalyCustom Add-in Development

"MSOfficeAddin is a true professional team that understands its craft. Very much enjoyed working with them. Even when my schedule got in the way, they accommodated it and were understanding."

M
Matt GersbachAustraliaOffice Add-in Development

"I had the pleasure of working with MSOfficeAddin, and I can confidently say that their expertise has been exceptional. They took the time to truly understand our needs, ensuring that the solutions provided were tailored and effective. Communication throughout the process was clear, timely, and always professional."

T
Techpreneur MRUMauritiusCustom Add-in Solutions

"An experienced and professional developer. Thank you for the good work!"

W
WebzollnerRepeat Client · GermanyOffice Add-in Development

"Great to work with, took time to understand requirements, and delivered to timetable!"

G
Graham ClarkRepeat Client · United KingdomOffice Add-in Development

"MSOfficeAddin helped me solve our pain and did it very fast and easy. We're working with them to further enhance and improve our business."

C
Casper SankoRepeat Client · DenmarkBusiness Automation Add-in

"Amazing seller, and amazing developer. Great communication to ensure all requests were met, and project was completed as specified. MSOfficeAddin went above and beyond, and worked long hours to complete this project. This was a great experience."

R
Revlis01CanadaCustom Add-in Development

"Great communication, delivered ahead of schedule and helped with questions I had. Will contact again for other projects, thank you!!!"

J
Jose MartinezUnited StatesOffice Add-in Development

"You will be happy with the MSOfficeAddin team's services. They did an amazing job understanding user requirements and executing them effectively."

A
Abdul HakimUnited StatesOffice Add-in Development

"Perfect work as always. Great experience!"

M
Michael ThiemeGermanyOffice Add-in Development

"The MSOfficeAddin team did an outstanding job developing our plugin. They understood our requirements perfectly, communicated clearly, and delivered high-quality results on time. Highly recommended!"

N
Nabi UllahSwitzerlandCustom Plugin Development

"Delivered exactly what we agreed on. The tool is working perfectly fine."

C
Christoph KutzGermanyOffice Add-in Development

"Delivery within time, clean and well-commented code, extra adjustments, and full deployment on my server. Very professional work and excellent communication."

M
Marjolein MosNetherlandsAdd-in Development & Deployment

"If you're looking for someone to help you achieve what you need — the MSOfficeAddin team are the Add-in experts! They developed a fully functional add-in and successfully implemented it in my M365 business account, allowing me to interact with the entire Office Suite and automate as much as possible. I'm very satisfied with their work and will contact them again in the future for sure."

R
RobertoRepeat Client · SpainM365 Automation Add-in

"The MSOfficeAddin team has been incredible and provided excellent work on the first delivery."

H
Hamid ShafiUnited KingdomOffice Add-in Development

"Exceptional experience working with this developer. Their coding expertise greatly contributed to the project's success."

D
DirkGermanyOffice Add-in Development

"It was a pleasure working with the MSOfficeAddin team. They completed the work quickly and demonstrated strong expertise in Office Add-ins and Microsoft APIs."

D
Danish AliAustraliaOffice Add-in Development

"The MSOfficeAddin team understood our requirements for the Outlook plugin we needed. Even with the time zone differences they were able to talk and work around our schedule. Would definitely recommend and use their services again in the future."

G
GoMax SolutionsRepeat Client · CanadaOutlook Add-in Development

Frequently asked questions

How do I hire Microsoft developers for custom Office plugins?
Contact us at info@msofficeaddin.com or via the /contact page. We are a Microsoft Partner Network member with 250+ Office Add-in projects delivered over 5+ years. Project quotes are returned within 24 business hours.
What is the difference between an Office Add-in and a COM Add-in?
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.
How much does it cost to develop a custom Office Add-in?
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.
Can you publish my Office Add-in to Microsoft AppSource?
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.
Which Office apps do you build add-ins for?
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.
Can you migrate our old VSTO or COM add-in to Office.js?
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.

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