Custom API Integration for Office Add-ins
Connect any REST, GraphQL, or SOAP API to your Excel, Outlook, or Word add-in. We handle auth, error handling, and data mapping so your add-in talks to any backend system.
Integration at a Glance
250+ Projects
delivered across integration builds
7 Integration Types
SAP, AI, CRM, Power BI and more
5+ Years
building Office add-in integrations
Free Discovery Call
to scope your integration project
What We Build Into Your Custom API Integration
REST API Integration
GET, POST, PUT, PATCH, DELETE. We handle all REST methods and map responses to Excel ranges, Outlook fields, or Word content controls.
GraphQL Support
We write typed queries and mutations against GraphQL APIs and pipe results into Office add-ins with proper loading and error states.
SOAP & Legacy Endpoints
Older enterprise systems often expose SOAP APIs. We parse WSDL files and build the SOAP client layer your add-in needs.
OAuth 2.0 & SSO
We implement OAuth 2.0 authorization code flows, PKCE, and Microsoft SSO so users authenticate once and the add-in handles tokens automatically.
Data Mapping & Transformation
API responses rarely match what Excel expects. We transform, flatten, and map data structures so the right values land in the right places.
Rate Limiting & Retry Logic
We build exponential backoff, request queuing, and user-facing progress indicators so your add-in handles API limits gracefully.
How the Integration Project Works
- 1
API Review
We review your API documentation, test endpoints, and identify any auth, CORS, or rate-limit constraints that will affect the add-in build.
- 2
Auth Implementation
We implement the right authentication method for your API, whether OAuth 2.0, API keys, or SSO, and confirm tokens are handled securely within the Office add-in context.
- 3
Data Mapping
We map your API response structure to the Office data model, whether Excel ranges, Outlook fields, or Word content controls, so output lands exactly where it should.
- 4
Add-in Build & Testing
We build the full Office.js add-in, test against live and staging API endpoints, and cover error states including timeouts, empty responses, and auth failures.
- 5
Deployment
We deploy the add-in via Microsoft Admin Center for internal rollout or prepare it for AppSource submission if wider distribution is required.
Custom API Integration: Common Questions
Yes. We connect add-ins to internal APIs hosted on private networks, VPNs, or corporate intranets. We handle CORS configuration, network routing, and any auth requirements your IT team specifies.
Ready to Connect Custom API to Microsoft 365?
We scope every integration project on a free discovery call. No commitment, just a clear picture of what the build involves and what it will cost.