Migrate VSTO & VBA to Modern Web Add-ins
Still tied to a Windows-only VSTO add-in or a sprawling VBA macro? We migrate legacy Office solutions to modern, cross-platform web add-ins built on Office.js — preserving everything your team relies on while unlocking Mac, web, and instant updates.
The Case for Moving Off Legacy Office Code
Cross-Platform Reach
Web add-ins run on Windows, Mac, Office on the web, and mobile — not just Windows desktop like VSTO and VBA.
Instant Updates, No Installs
Ship fixes and features from the server. No MSI rollouts, ClickOnce prompts, or per-machine installs.
AppSource Distribution
Publish publicly on Microsoft AppSource or push privately through centralized deployment.
A Safer Sandbox
The Office.js runtime is sandboxed and permission-scoped, which enterprise security teams prefer.
Future-Proof
Microsoft is investing in web add-ins going forward. Migrating protects your tool from a shrinking platform.
A Modern Stack
Move from aging COM/.NET desktop code to HTML, TypeScript, and frameworks your team can hire for.
What Changes When You Migrate
Your VSTO / VBA Today
Windows-only, install-based
- Runs only on Windows desktop Office
- Requires installers, updates, and admin rights
- Aging COM/.NET or VBA codebase
- Harder to hire and maintain for
- No path to Mac, web, or mobile users
Modern Web Add-in
Cross-platform, cloud-updated
- Runs on Windows, Mac, web, and mobile Office
- Updates instantly from the server — no installs
- Modern HTML/TypeScript stack
- Easy to hire, extend, and maintain
- Distributable via AppSource or centralized deployment
A Low-Risk Migration Path
Audit & Assess
We review your existing VSTO/VBA solution, its dependencies, and how your team actually uses it.
Map the Features
Every feature is mapped to a modern equivalent, flagging anything the web API handles differently.
Re-Architect
We design a clean web add-in architecture — UI, backend services, and integrations — that fits your workflow.
Build & Migrate
We rebuild the logic on Office.js, porting business rules faithfully and modernising where it helps.
Test Across Platforms
Rigorous testing on Windows, Mac, and the web ensures parity with — or improvement on — the original.
Deploy & Decommission
We deploy via AppSource or centralized deployment, then help you retire the old add-in cleanly.
From Legacy Solutions to Modern Add-ins
VSTO Add-ins
Excel, Word, Outlook, and PowerPoint VSTO solutions built in C#/.NET.
VBA Macros
Legacy macro workbooks and templates rebuilt as maintainable web add-ins.
COM Add-ins & Automation
COM-based customizations and Office automation moved to the modern API surface.
Custom Ribbons & Task Panes
Ribbon buttons, task panes, and dialogs re-created with the Office UI model.