Since its introduction in 1998, Visual Basic 6.0 (hereinafter VB6) has been adopted in every type of core business system for Japanese enterprises—including sales management, inventory control, and accounting—due to its ease of development and high productivity. However, with the evolution of operating systems, its role is finally coming to an end.

While VB6 has long supported operations on the front lines as a so-called “legacy system,” an increasing number of companies have begun considering migration in recent years due to the end of support and other factors.

Generally, migrating to VB.NET, the legitimate successor to VB6, has been considered the better choice. However, in today’s world where Digital Transformation (DX) is a critical imperative, why not consider options other than just migrating to VB.NET?

Drawing on our track record of handling numerous VB6 migration projects, we will explain the “optimal migration destinations” you should be considering right now.

Reasons Why You Must Migrate VB6 (Reconfirmation and Business Risks)

Before discussing migration destinations, let’s organize the four facts behind why migration from VB6 is necessary.

1. End of Support for Windows 10

With the end of support for Windows 10 in October 2025, the OS environment where VB6 can operate stably has been lost. Under the successor environment, Windows 11, the guarantee of VB6 operation is limited, and the risk of compatibility issues—such as screen layout corruption and functional failure—is increasing.

2. No Security Patches and Vulnerabilities

Since support for the language itself has ended, no patch fixes will be provided even if new vulnerabilities are discovered. Furthermore, VB6’s standard communication protocols (such as SSL 3.0) do not meet modern security standards, so continuing to use them poses significant information security and compliance challenges.

This is not merely a technical issue, but a problem involving corporate responsibility (legal risk) regarding customer data and confidential information handled by the system. Information leaks after support has ended could have a devastating impact on management.

3. Incompatibility with 64-bit Environments and Latest Hardware

Drivers for current OSs and peripherals (such as printers and handheld terminals) are standardizing on 64-bit. VB6, being a 32-bit application, is increasingly unable to link properly with these latest hardware environments, leading to potential operational disruptions when equipment needs to be replaced.

Decline and Aging of Maintenance Engineers

While experienced VB6 developers are aging and reaching retirement, there are almost no young engineers learning VB6 from scratch. In the domestic talent market, securing engineers capable of maintaining or modifying existing systems is becoming more difficult every year.

Thorough Comparison: The 3 Major Destinations for VB6 Migration and Selection Criteria

Now to the main topic. You are thinking about migrating from VB6, but what options are actually available?

Option 1: Migration to VB.NET (Straight Conversion / Re-hosting)

The first option usually considered is migration to VB.NET, which is also a Microsoft product and the successor language to VB6. This method involves converting existing source code using conversion tools, commonly referred to as “Straight Conversion” or “Re-hosting.”

【Merits】 The greatest advantage is that since VB.NET is the successor language inheriting the VB6 language specifications, migration conversion tools and know-how can be utilized. By using third-party tools that inherit the technology of the Microsoft Official Upgrade Wizard (now discontinued), it is possible to mechanically migrate source code to the new environment.

Another merit is the ability to carry over existing business logic without breaking it. In legacy systems that have been running for over 20 years, “black box” situations—where specifications no longer exist, or the person in charge has retired and no one understands the meaning of the calculation formulas—are frequent occurrences. With conversion to VB.NET, the likelihood of maintaining calculation logic and business rules through mechanical replacement is high. As a result, costs and development time can be kept lower compared to other development methods due to the reduction in man-hours.

【Points of Caution】 In Microsoft’s technology roadmap, the current core of innovation has shifted to languages like C#. While VB.NET continues to be supported as a stable technology that values past assets, its position regarding new feature additions and evolution is more conservative compared to C#.

While it is very suitable for the purpose of “moving current operations as-is to a stable environment,” you must consider that technical choices may be somewhat narrowed if you wish to actively incorporate AI integration or the latest cloud technologies in the future.

Additionally, it is generally said that the range covered by conversion tools is limited, and about 50% of the total process requires manual correction and testing by engineers. The perception that “it will be finished easily because there is a tool” is dangerous.

Option 2: Modern Rebuild with C# / Web Languages (Promoting DX)

This method involves redefining specifications from scratch and rebuilding the system using modern standard languages like C# or JavaScript. In many cases, this involves converting to a Web-based system.

【Merits】 The biggest merit is gaining both a sustainable development structure for the future and business scalability that is resilient to change.

Regarding human resources, Web-based languages like C# and JavaScript are mainstream in the current engineer market. Adopting these makes it easier to secure young talent to handle future maintenance and operations. As the aging of VB technicians progresses, being able to fundamentally resolve the risk of personalization—where “the system exists, but there is no one who can fix it”—is an extremely large advantage for long-term corporate management.

Furthermore, by converting to a Web system, you are freed from traditional client PC management and can immediately adapt to flexible working styles such as remote work. Integration with the latest AI technologies and external cloud services becomes smoother, allowing the system to evolve from a mere business processing tool into “aggressive DX” that utilizes data to generate new profits.

【Points of Caution and Measures】 Because it is a rebuild, it is not rare for costs and duration to be more than double that of a migration to VB.NET. Also, confusion on the front lines due to changes in screens and usability is expected. While pushback from the field is an unavoidable challenge, a rebuild is equivalent to redoing requirements definition; therefore, it is essential to have an attitude of changing the organizational culture with strong leadership, viewing it as “Business Process Re-engineering” led by management.

Option 3: Switching to SaaS or Low-Code Platforms

There is also the option of using existing SaaS or low-code platforms, starting from the perspective of “Is it really necessary to develop a custom system in-house?”

【Merits】 Implementation speed is overwhelmingly fast, and compliance with legal revisions—such as the Invoice System—can be left to the vendor. The cost is also significantly lower compared to rebuilding from scratch.

In recent years, the movement to replace systems using low-code platforms like Kintone or Microsoft Power Platform has been active. Since development is possible with little specialized programming knowledge, there is the merit of making it easier to perform business improvements and modifications.

【Points of Caution and Measures】 You need to carefully assess whether your company’s business flow matches the functions of that SaaS. To prevent failures like “we thought it looked good, but it lacked necessary functions,” prior verification is crucial. Also, do not forget that it is necessary to review your company’s unique methods to date and change your business flows to fit the tool.

Summary

In this article, we explained the risks of continuing to use VB6 and the main migration destinations. We have supported numerous projects at our company, and the “correct answer” varies depending on the company’s situation—from cases prioritizing operational stability by migrating to VB.NET, to cases driving DX at once by rebuilding in C#.

The important thing is not just “replacing an old system,” but selecting a migration destination from the perspective of “how you want your company to be in 5 or 10 years.”

Please select the optimal route by comparing not only budget and delivery time but also your company’s future direction.

We will propose the method that fits your project

As a leading Japanese IT solution company with approximately 20 years of experience in Vietnam offshore development, we have been providing software and system development services. Please feel free to consult us when considering offshore development.

Vietnam Offshore Development