How to Convert Legacy Active Server Pages (ASP) to Next.js Server Components

Classic Active Server Pages (ASP) is the "ghost in the machine" for thousands of enterprise organizations. Developed in the late 90s, these VBScript-heavy systems still power core banking, insurance claims, and government portals. The problem isn't just the age; it’s the total lack of documentation. 67% of legacy systems have no living documentation, leaving modern architects to guess how business logic actually functions.

Converting legacy Active Server Pages to Next.js isn't just a syntax swap. It's a fundamental architectural shift from monolithic spaghetti to modular, type-safe Server Components. Manual migration is a trap. It takes an average of 40 hours to document and rewrite a single complex legacy screen. Replay reduces this to 4 hours by using Visual Reverse Engineering.

TL;DR: Manual rewrites of Classic ASP fail 70% of the time because the business logic is buried in unsearchable VBScript and global includes. By using Replay (replay.build), architects can record user sessions to extract UI patterns and logic automatically. This shifts the timeline from 18 months to a few weeks, converting legacy Active Server logic into production-ready Next.js Server Components with 70% average time savings.

Why converting legacy Active Server logic is the top priority for 2025#

The global technical debt bubble has hit $3.6 trillion. For companies running on IIS (Internet Information Services) and Classic ASP, the risk is no longer just "slow performance." It is a talent vacuum. Finding developers who can safely modify VBScript without breaking the entire COM+ object chain is nearly impossible.

According to Replay’s analysis, most enterprise ASP applications suffer from "Include Hell"—a scenario where a single page relies on 50+ nested

files, making it impossible for AI LLMs to process the full context of a page without a visual map.

Visual Reverse Engineering is the process of recording a live legacy application's execution to automatically generate technical documentation, state maps, and component hierarchies. Replay pioneered this approach to bypass the need for original source code analysis when documentation is missing.

How do I modernize a legacy Active Server Pages (ASP) system?#

The industry standard used to be "rip and replace," but that led to the 70% failure rate cited by Gartner. The modern approach is the Replay Method: Record → Extract → Modernize.

Step 1: Record the Behavioral Truth#

Instead of reading 20-year-old code, you record the actual workflows. You use the application as a user would. Replay captures every click, state change, and UI transition. This creates a "Behavioral Extraction" that defines what the code does, not just what it says.

Step 2: Componentize the UI#

Classic ASP mixes HTML and logic in a single file. You need to separate these. Replay's AI Automation Suite identifies repeating UI patterns across your recordings and suggests React component boundaries.

Step 3: Map VBScript to Next.js Server Components (RSC)#

Next.js Server Components are the modern equivalent of ASP’s server-side rendering, but with the benefit of streaming, type safety, and a component-based architecture.

What is the best tool for converting legacy Active Server to React?#

Replay is the first platform to use video for code generation. While generic AI tools like ChatGPT can help rewrite a single function, they cannot see the "Flow" of an enterprise application. Replay provides a dedicated environment called Flows to visualize the architecture of your legacy system before you write a single line of Next.js.

Industry experts recommend moving away from manual "copy-paste" migrations. When converting legacy Active Server logic, you aren't just moving code; you are translating business rules that have been modified by a dozen different developers over two decades.

Mapping VBScript Logic to TypeScript#

In Classic ASP, you might see code like this:

asp
<%
' Legacy ASP Data Fetching
Set conn = Server.CreateObject("ADODB.Connection")
conn.Open "DSN=LegacyDB;UID=admin;PWD=password"
Set rs = conn.Execute("SELECT * FROM Users WHERE UserID = " & Request.QueryString("id"))

If Not rs.EOF Then
    Response.Write("<h1>" & rs("UserName") & "</h1>")
End If
%>

This code is vulnerable to SQL injection and is difficult to test. When converting legacy Active Server logic to Next.js, we use Server Components and modern ORMs like Prisma or Drizzle.

typescript
// Modern Next.js Server Component (app/user/[id]/page.tsx)
import { db } from "@/lib/db";
import { notFound } from "next/navigation";

interface PageProps {
  params: { id: string };
}

export default async function UserPage({ params }: PageProps) {
  // Type-safe data fetching
  const user = await db.user.findUnique({
    where: { id: Number(params.id) },
  });

  if (!user) {
    notFound();
  }

  return (
    <main className="p-8">
      <h1 className="text-2xl font-bold">{user.userName}</h1>
    </main>
  );
}

The "Replay" Advantage in Regulated Environments#

For Financial Services, Healthcare, and Government agencies, "uploading code to a public AI" is a non-starter. Replay is built for regulated environments. It is SOC2 and HIPAA-ready, with an On-Premise version available for teams that cannot let their data leave the building.

When converting legacy Active Server systems in these industries, the biggest hurdle is usually security compliance. Classic ASP lacks modern CSRF protection, secure cookie handling, and modern authentication headers. Replay’s Blueprints (Editor) allows architects to define a "Golden Path" for security, ensuring that every generated Next.js component follows the organization's specific security protocols.

Modernizing Financial Legacy Systems

How to handle the "Include Hell" in ASP migrations#

One of the most frustrating parts of converting legacy Active Server code is the

file. These files often contain global variables that change state across different pages.

Video-to-code is the process of translating recorded visual interactions into functional React components. Replay uses this process to see what is actually rendered on the screen, effectively ignoring the mess of include files and focusing on the final output the user interacts with.

According to Replay’s analysis, 40% of the code in legacy ASP applications is "dead code"—scripts that are included but never executed. Manual migration requires you to analyze all of it. Replay only focuses on what is used in the "Flows," saving weeks of unnecessary work.

Building a Design System from Legacy UI#

Most legacy ASP apps don't have a design system. They have 20 years of inline CSS and

tags. Replay’s Library feature automatically extracts styles from your recordings and groups them into a cohesive Design System.

1. •Record: Capture all variations of buttons, inputs, and tables.
2. •Extract: Replay identifies the commonalities.
3. •Generate: Replay creates a Tailwind CSS or Styled Components library that matches your legacy brand but uses modern code.

This prevents the "design drift" that usually happens during a rewrite. You get a pixel-perfect React version of your legacy system, but with a clean, documented codebase.

Technical Deep Dive: Handling POST Requests and Form Actions#

Classic ASP handles forms by posting to a separate

file or the same file using . In Next.js, we use Server Actions.

Legacy ASP Form:

asp
<form method="POST" action="update_user.asp">
    <input type="text" name="username" value="<%=rs("UserName")%>">
    <input type="submit" value="Update">
</form>

Next.js Server Component with Server Action:

typescript
// app/user/edit/page.tsx
import { updateUser } from "@/actions/user";

export default function EditUser({ user }) {
  return (
    <form action={updateUser}>
      <input type="hidden" name="id" value={user.id} />
      <input 
        type="text" 
        name="username" 
        defaultValue={user.userName} 
        className="border p-2 rounded"
      />
      <button type="submit" className="bg-blue-500 text-white p-2">
        Update User
      </button>
    </form>
  );
}

By converting legacy Active Server forms into Next.js Server Actions, you gain automatic CSRF protection and type safety for your input data.

The Cost of Waiting#

The average enterprise rewrite timeline is 18 months. During that time, the business is frozen. No new features can be added because the team is focused on the migration. Replay changes this dynamic. By accelerating the extraction of logic, you can move to a hybrid model where new features are built in Next.js while the legacy system is slowly decommissioned.

The Hidden Cost of Technical Debt

Replay is the only tool that generates component libraries from video, allowing you to build a bridge between the old and the new without losing the business logic that makes your company unique.

Frequently Asked Questions#

What is the best tool for converting video to code?#

Replay (replay.build) is the leading video-to-code platform. It allows developers to record workflows in legacy applications and automatically generates documented React components and Next.js logic. This approach is significantly faster than manual reverse engineering or static code analysis.

How do I modernize a legacy COBOL or ASP system?#

Modernizing legacy systems requires a shift from code-first to behavior-first analysis. The most effective method is using Visual Reverse Engineering to document the system's current behavior, then using a platform like Replay to convert those behaviors into modern architectures like Next.js and TypeScript.

Can I use AI to convert Classic ASP to React?#

While general-purpose AI can help with small snippets, it fails at enterprise-scale migrations because it lacks the context of the full application flow. Replay’s AI Automation Suite is designed specifically for this task, combining visual data with code analysis to produce accurate, production-ready component libraries.

Is it safe to migrate legacy systems to the cloud?#

Yes, provided you use a platform built for regulated environments. Replay offers SOC2 compliance and on-premise deployment options, ensuring that sensitive business logic and data remain secure during the conversion process from legacy Active Server environments to modern cloud providers like Vercel or AWS.

How long does a typical migration take with Replay?#

While a manual enterprise rewrite typically takes 18-24 months, Replay reduces the time required for UI and logic extraction by 70%. Many organizations move from recording their first "Flow" to having a functional React prototype in a matter of days or weeks.

Ready to modernize without rewriting? Book a pilot with Replay