Migrate — the same application, on a recent version. You keep everything in it, including twenty years of business logic.

Rebuild — start again, possibly on a different technology. You are rid of the legacy, but also of everything that was in it without anyone realising.

Open up — let the application run as it runs, and offer only the parts needed outside the office through the browser.

Four questions that decide it

What is in there that exists nowhere else? Most applications that have run for fifteen years contain business logic nobody can fully explain any more. Rebuilding means rediscovering that logic. That is often more expensive than the construction itself.

Who uses it, and where? If everyone sits in the office, there is little reason to open anything up. The moment customers, suppliers or staff on the road need access, that changes.

How much still changes? An application that has been stable for years gains little from a rebuild. One that grows every month benefits from being maintainable.

What is the risk of standstill? If the application fails tomorrow and nobody can repair it, that is a different conversation from one where you have years of runway.

When each path wins

• Migrating wins almost always when the application does what it should and the only problem is the version. It is the cheapest path and the easiest to estimate.
• Opening up wins when the application works well but sits in the wrong place. You leave the core alone and the result shows quickly.
• Rebuilding rarely wins on its own. Usually only when there is also a genuine reason to change the process itself.

Know first, then choose

All three paths are defensible. Which is right for you depends on what is inside your application — and that is usually exactly what nobody fully knows any more. Which is why this conversation starts with an inventory, not with a quotation.

That inventory is the starting point of our 4D assistance, and produces a reasoned answer instead of a guess.