Blog Post

Custom Office Add-ins for Business


Raspal Chima -

Most people never use the full range of features that are available within the Microsoft Office Suite. At the same time, there is always some feature or tool that users wished they had within the Suite to make life easier and potentially save on hours of work preparing documents. This is where add-ins for Office 365 can help.

Add-ins-Blog-Blueberry Consultants

How much of our working lives do we spend in Outlook, or going from one Office app to another to complete a multifaceted task? It might be a rhetorical question, but it goes without saying that being able to work between Office apps in a seamless and streamlined way would be nothing short of revolutionary. This is where the new functionality offered by the Office Add-ins system opens the door for customisation – to bring line-of-business applications inside Office 365.

What is an Office Add-in?

So, what is an Office Add-in? Basically, it’s an extension that appears in the top ribbon of an Office app, designed to extend the features of that application – making it more powerful, and potentially allowing it to interact with content in other Office documents, or other sources. For example, an add-in could reference Outlook data and display the information, or access professional looking templates designed around a corporate style, or automatically sign important documents with a digital signature – the list of what’s possible is almost endless.

One of the big benefits of using add-ins is that there’s no need to leave the Office application you’re currently using in order to complete additional tasks in the Office Suite. This means workflows can be implemented in Outlook or SharePoint, for example, to automate processes that result in streamlining tasks that would otherwise involve entering the same data again somewhere else.

Add-ins can also improve collaboration between people on the same document in Word, Excel, or PowerPoint, whilst maintaining live synchronisation so that everyone can remain on the same page.

What’s made this possible was the launch of Microsoft’s Office 365 in 2011 and the new Office Add-ins platform, which brought big changes to the way Office Add-ins were developed. The old COM and VSTO add-ins that were being used in earlier Office integration solutions ran code on the user’s device or in the Office client, and could be buggy, causing an app to hang. The new Office Add-ins are much more stable and use a different approach, which we discuss next.

Extending Office With Add-ins

There are two ways to get add-ins that extend and interact with Office applications. The first is to browse the list of Office Add-ins in your app, or search for one in Microsoft’s AppSource store. Some of these will be free, others have paid upgrades.

The second is to build an add-in that brings new features to an Office program, using the skills of a developer. Since the launch of Office 365, Microsoft has made it easier for devs to create new add-ins or upgrade existing ones. They did this by moving developers to a new cross-platform JavaScript-based add-in model. This model means the same add-in can supposedly run wherever Office is being used, without having to modify the code – on smartphones, PCs, and the web. In practice, it’s not quite that straightforward, unless it’s the same version of Office being used – more on this later.

The new add-in approach has been developed using a shared set of technologies (which would eventually become the Microsoft Graph), linking Office apps in a way that allows data from one programme to be used by another.

In essence, each add-in is a small web application that runs on a server and behaves similarly to any other browser programme.

How Add-ins Work

Add-ins extend the Office application by providing tools to their host programme – such as hooks for ribbon buttons and menu commands – and are more secure than the old COM add-ins since the add-on loads and operates in its own safe sandbox, without access to the rest of the system.

Apps can be shared through Microsoft’s AppSource store, either for free, or paid-for with a one-time fee or a monthly subscription.

And if your requirement is not addressed by existing Office Add-ins, one can be developed on a bespoke basis by a developer to improve productivity and team collaboration.

To create a bespoke Office Add-in, devs can now use familiar web technologies such as HTML, CSS, and JavaScript to extend and interact with Word, Excel, PowerPoint, OneNote, Project, etc., ensuring the solution will run in Office across multiple platforms.

The Office Add-in includes just two basic components: an XML manifest file, plus your own web application, which is usually hosted on a web server, or web hosting service. The manifest defines the various settings, including how your add-in integrates with Office clients.

Technical Considerations

Blueberry has created a number of bespoke Office Add-ins for its clients, to fit their unique business requirements.

In our experience, whilst Microsoft is continuing to extend the functionality of add-ins, there are limitations to what can be done, particularly when integrating with the Office application itself. Some technical considerations to bear in mind when developing bespoke add-ins include:

Office Versions
There are many versions of Office on several platforms, and they don’t all support every API in the Office JavaScript API. If your add-in is being written for users outside of your organisation, you won’t have control over the version of Office users have installed. So, depending on what the add-in is designed to do, it may be necessary to tailor some of the features, depending on the version of Office installed by the user.

Support for IE11
If you plan to market your Office Add-in through AppSource, or you plan to support older versions of Windows and Office, your add-in must work in the embeddable browser control that is based on Internet Explorer 11 (IE11). Internet Explorer 11 doesn’t support some HTML5 features, such as media, recording, and location – so if your add-in must support Internet Explorer 11, then you can’t use these features.

Hosting Domain
Office Add-ins are hosted in a browser control running web pages hosted on a server. Because of this, there needs to be careful consideration on where those web pages are hosted; if they are going to be hosted on another domain, then some additional steps need to be taken to allow it to work.


At Blueberry, we have a thorough understanding of the Microsoft Office platform, and we have the technical experience to develop robust Office Add-ins quickly to improve staff productivity and team communication.

If what you need in an Office Add-in isn’t available ‘off-the-shelf’, Blueberry can develop one tailored to your unique business needs. Just give us a call to get the ball rolling!

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Don't worry if you don't know about the technical stuff, we will happily discuss your ideas and advise you.