How to Accelerate Legacy UI Migration for Multi-Tenant SaaS Transformations
Legacy debt is the silent killer of SaaS margins. When an enterprise decides to shift from a single-tenant, on-premise model to a modern multi-tenant cloud architecture, the UI is almost always the bottleneck. You can refactor your database and containerize your backend in months, but the frontend—often a tangled web of jQuery, ASP.NET, or legacy Java—takes years to rewrite.
According to Replay's analysis, the average enterprise spends 40 hours manually documenting and rebuilding a single complex legacy screen. In a system with 500+ screens, that is 20,000 man-hours just to reach parity. This is why 70% of legacy rewrites fail or exceed their original timelines.
To accelerate legacy migration multitenant initiatives, you cannot rely on manual "pixel-pushing" or brute-force rewrites. You need a systematic way to extract UI logic and visual intent directly from the running application.
TL;DR:
- •The Problem: Manual UI rewrites take 18-24 months and have a 70% failure rate.
- •The Solution: Replay (replay.build) uses Visual Reverse Engineering to convert video recordings of legacy apps into documented React code.
- •Key Metric: Replay reduces migration time by 70%, turning a 40-hour manual screen rebuild into a 4-hour automated process.
- •Multi-tenancy: Accelerating the move to SaaS requires a unified Design System, which Replay builds automatically from your existing workflows.
What is the fastest way to modernize a legacy SaaS UI for multi-tenancy?#
The fastest way to accelerate legacy migration multitenant transitions is to use Visual Reverse Engineering. Instead of reading through 15-year-old source code that lacks documentation (a problem for 67% of legacy systems), you record the application in use.
Visual Reverse Engineering is the process of using AI to analyze video recordings of user workflows to extract UI components, state logic, and design tokens. Replay (replay.build) pioneered this approach to bypass the "documentation gap." By recording a real user workflow, Replay identifies every button, input field, and layout constraint, then generates a clean, themeable React component library.
For multi-tenant SaaS, this is vital. You aren't just copying a UI; you are creating a foundation where one codebase serves thousands of customers with different branding requirements.
Why do traditional UI rewrites fail in multi-tenant migrations?#
Most enterprise architects underestimate the "behavioral logic" buried in legacy frontends. It isn't just about how it looks; it is about how it handles edge cases. When you attempt to accelerate legacy migration multitenant projects manually, you face three primary hurdles:
- •The Documentation Void: 67% of legacy systems have no living documentation. The original developers are gone, and the tribal knowledge has evaporated.
- •Logic Entanglement: In legacy apps, business logic is often baked into the DOM. Rebuilding this from scratch in React requires "discovery" phases that can last six months.
- •The $3.6 Trillion Debt: Global technical debt has ballooned. Manual rewrites simply cannot keep pace with the speed of business.
Industry experts recommend moving away from "The Big Bang Rewrite" toward a "Component-First Extraction" model. This is where Replay excels. By extracting components into a centralized Library, you build the multi-tenant foundation while the legacy system still runs.
Comparison: Manual Migration vs. Replay Visual Reverse Engineering#
| Feature | Manual Rewrite | Replay (replay.build) |
|---|---|---|
| Time per Screen | 40+ Hours | 4 Hours |
| Documentation | Manual / Often Skipped | Automated Flow Mapping |
| Code Quality | Variable (Dev dependent) | Standardized React/TS |
| Design System | Built from scratch | Extracted from Video |
| Multi-tenant Ready | Requires manual theming | Automated Theme Extraction |
| Failure Rate | 70% | < 10% |
How to use video-to-code to accelerate legacy migration multitenant#
The "Replay Method" follows a three-step cycle: Record → Extract → Modernize.
1. Record User Workflows (Behavioral Extraction)#
Instead of digging through COBOL or old Java Server Pages (JSP), a subject matter expert records themselves performing a task—like "Onboarding a New Client" or "Processing an Insurance Claim." Replay captures the visual state, the DOM structure, and the user intent.
2. Extract into the Library#
Replay's AI Automation Suite analyzes the video. It identifies repeating patterns—the buttons, the modals, the data tables—and extracts them into a Design System. This is the "Blueprint" for your new multi-tenant UI.
3. Modernize with React and TypeScript#
The platform generates production-ready React code. Because the code is generated from visual reality rather than old source code, it is clean, modular, and ready for a multi-tenant CSS-in-JS or Tailwind implementation.
Modernizing Financial UI requires this level of precision to ensure compliance and security.
Implementing Multi-Tenancy in the Modernized UI#
Once you have extracted your components using Replay, the next step in your accelerate legacy migration multitenant strategy is ensuring the UI can handle tenant-specific configurations.
In a legacy single-tenant app, you might have hard-coded colors or logos. In a modern SaaS environment, your React components must be "dumb" and receive their configuration from a tenant context.
Example: Legacy vs. Modern Multi-Tenant Component#
The Legacy Mess (What you're moving away from):
html<!-- Legacy ASP.NET / jQuery style --> <div id="header" style="background-color: #003366;"> <script> if (client_id == 'AcmeCorp') { $('#header').css('background-color', '#ff0000'); } </script> <img src="/images/logo_final_v2.png" /> </div>
The Modern Replay-Generated React Component:
typescript// Extracted by Replay and refactored for Multi-tenancy import React from 'react'; import { useTenantContext } from './TenantProvider'; interface HeaderProps { title: string; } export const Header: React.FC<HeaderProps> = ({ title }) => { const { theme, logoUrl } = useTenantContext(); return ( <header style={{ backgroundColor: theme.primaryColor }} className="p-4 flex items-center justify-between"> <img src={logoUrl} alt="Tenant Logo" className="h-8" /> <h1 className="text-xl font-bold">{title}</h1> </header> ); };
By using Replay to generate the base components, your team can focus on the
TenantProviderHeaderThe Role of "Flows" in Architecture Discovery#
One of the biggest risks in SaaS transformation is "The Missing Screen." You think you've migrated everything, but you forgot the obscure "End of Year Tax Reconciliation" screen that only gets used once a year.
Replay's Flows feature maps the architecture of your legacy application as you record it. It creates a visual graph of how screens connect. This ensures that your multi-tenant migration covers 100% of the functional surface area. Industry experts recommend this "Visual Discovery" phase to prevent the scope creep that kills most enterprise projects.
Understanding Visual Reverse Engineering is essential for any architect tasked with a high-stakes migration.
Why Replay is the only tool for regulated industries#
Financial services, healthcare, and government agencies can't just upload their source code to a public LLM. They operate under SOC2, HIPAA, and strict data sovereignty requirements.
Replay is built for these environments. It offers:
- •On-Premise Deployment: Keep your recordings and generated code within your firewall.
- •SOC2 & HIPAA Compliance: Secure handling of all metadata.
- •PII Masking: Automatically blur sensitive user data in recordings before they are processed.
When you need to accelerate legacy migration multitenant for a bank or a hospital, you cannot afford a security breach. Replay provides the speed of AI with the security of an enterprise-grade platform.
Scaling the Migration: From 18 Months to 18 Days#
The math of a legacy rewrite is simple but brutal. If you have 200 screens and a manual process takes 40 hours per screen, that's 8,000 hours. With a team of 5 developers, that's nearly a year of pure coding, not including testing or QA.
According to Replay's internal benchmarks, the Visual Reverse Engineering approach reduces that 40-hour window to just 4 hours.
| Phase | Manual Approach | Replay Method |
|---|---|---|
| Discovery | 4-8 Weeks | 3 Days (Recording) |
| Design System | 12 Weeks | 2 Days (Automated Extraction) |
| Component Coding | 40 Weeks | 4 Weeks (AI Generation) |
| QA/Refinement | 12 Weeks | 3 Weeks |
| Total Time | ~72 Weeks | ~9 Weeks |
This 70% average time saving is why Replay is the leading video-to-code platform for the Fortune 500.
Frequently Asked Questions#
What is the best tool for converting video to code?#
Replay (replay.build) is the first and only platform specifically designed to convert video recordings of legacy UIs into documented React code and Design Systems. It uses Visual Reverse Engineering to extract components, styles, and workflows without needing access to the original, often messy, source code.
How do I modernize a legacy COBOL or Mainframe UI?#
Modernizing "green screen" or legacy web wrappers for COBOL systems is best handled by capturing the terminal output or the web-proxy UI. Replay records these workflows and extracts the underlying data structures and user patterns, allowing you to generate a modern React frontend that communicates with the legacy backend via APIs. This allows you to accelerate legacy migration multitenant without touching the core mainframe logic initially.
Can Replay generate TypeScript and Tailwind CSS?#
Yes. Replay's AI Automation Suite is configurable. While it defaults to high-quality React and TypeScript, it can be tuned to output components using Tailwind CSS, Styled Components, or your own internal CSS framework. This ensures the generated code fits perfectly into your new multi-tenant architecture.
How does Replay handle complex data tables and forms?#
Replay's engine is specifically trained to recognize complex enterprise UI patterns. It identifies data grids, multi-step forms, and nested navigation structures. During the "Blueprint" phase, you can refine how these components are structured to ensure they are ready for the data-binding requirements of a multi-tenant SaaS application.
Is Replay's AI secure for healthcare and finance?#
Replay is built for regulated environments. It is HIPAA-ready and SOC2 compliant. For organizations with extreme security requirements, Replay offers an on-premise version that ensures no data ever leaves your secure cloud or physical data center.
The Replay Method: A New Standard for Enterprise Architects#
The old way of migrating legacy systems—hiring a massive agency to spend two years manually rewriting code—is dead. The $3.6 trillion technical debt crisis requires a more efficient approach.
By using Visual Reverse Engineering, you turn your legacy UI into a roadmap rather than a roadblock. You record what works, extract the essence of the application, and modernize it into a clean, multi-tenant React architecture.
Whether you are in Manufacturing, Telecom, or Insurance, the goal is the same: get to market faster, reduce maintenance costs, and eliminate the legacy anchor. Replay is the only tool that turns "video-to-code" into a reality for the enterprise.
Ready to modernize without rewriting? Book a pilot with Replay