Business Central extensions that survive every update

How Business Central extensions work

An extension is a compiled app file that holds AL objects. Table extensions add fields to existing tables. Page extensions place those fields on screens. New tables, pages, reports and codeunits carry anything that did not exist before. Your logic attaches to standard processes through events. Microsoft's code publishes those events at set points.

Nobody edits the base application, so Microsoft can update it underneath you. This is the main difference from older NAV versions. There, changes went into the standard objects. Every upgrade meant merging code by hand. You can also uninstall an extension. You choose whether its data stays.

Per-tenant Business Central extensions and marketplace apps

There are two families. A per-tenant extension is written for one customer. It is uploaded to that customer's environment on the Extension Management page. It can be as small as three fields and a validation rule. You own it, and it is nobody's product but yours.

A software vendor publishes a marketplace app for many customers. You install it from Microsoft's marketplace. It has passed Microsoft's checks. The publisher keeps it current. We compare both routes for each need. A mature app often beats writing and maintaining the same thing privately.

How we build Business Central extensions

Every extension starts as a written specification in business language. It says what the user does and what the system does in response. It also says how we will prove it works. We develop in Visual Studio Code against a sandbox. Objects follow a naming prefix and an assigned ID range. So they never collide with other apps.

Next, we write automated tests for posting and calculation logic. Then your users test the screens on a sandbox copy of production. We upload the app to the live environment only after sign-off. Source code, the specification and the test results sit together in a Git repository under your control.

Keeping Business Central extensions healthy through updates

Microsoft delivers two release waves a year and smaller updates in between. Before a major version arrives, we check each extension against it. Suppose an app would fail to compile. Then you can hold back the environment's update until the problem is solved. Administrators are notified. Doing nothing is not a safe option for long.

We recompile each extension against the preview version. We fix warnings about obsolete objects before they become errors. Then we rerun the automated tests. Telemetry in Application Insights shows which custom objects are slow or fail in daily use. So evidence guides maintenance, not complaints.

Mistakes we see in custom Business Central extensions

The most frequent problem is lost source code. The app runs, the developer has moved on, and nobody holds the project files. So even a one-line change becomes a rebuild. The second is one giant extension that holds every change ever requested. A small fix then needs a retest of the whole thing.

Others are quieter. Some copy logic from standard code instead of subscribing to an event. Others add fields without thinking about reports and APIs. A few have no upgrade code to carry data between versions. When we take over existing extensions, we read them and document what each does. Then we tell you which are worth keeping.

Business Central extensions: frequent questions

What is an extension in Business Central?

It is an app written in AL. It adds tables, fields, pages, reports or logic. Microsoft's base application stays unchanged. You install extensions per environment. You can update or remove each one on its own.

Will an extension break when Microsoft updates the system?

A well made extension usually keeps working. It uses published events and objects. Microsoft marks objects as obsolete well before it removes them. We test against preview versions. So we make any needed change before your environment updates.

Can extensions be installed in Business Central online?

Yes. You upload per-tenant extensions on the Extension Management page. You install marketplace apps from Microsoft's marketplace. We try both first in a sandbox environment. So testing always happens safely, away from live data.

How is an extension different from a customization?

In everyday speech they mean the same thing. Technically, configuration and personalization change settings and layouts without code. An extension is code. We try the first two before we propose the third, because code needs upkeep. That keeps your Business Central extensions few and useful.

What happens to our data if an extension is removed?

When you uninstall an extension, its data stays in the database by default. So reinstalling brings it back. Deleting the data is a separate, deliberate choice made in Extension Management. We export anything important before that step.

More on changing Business Central

Extensions are one way to shape the system. These pages explain development, customization and marketplace apps in more depth. Read them to see where Business Central extensions fit among your options. Then use the contact page to talk through a need. We will tell you whether setup, an app or an extension suits it best. For the product detail, see Microsoft Learn: customizing Business Central using extensions.