Manual Internationalization is Where Engineering Velocity Goes to Die

Manual internationalization (i18n) is a grind that breaks even the best engineering teams. You start with a legacy dashboard, thousands of hardcoded strings, and CSS layouts that shatter the moment a German word exceeds twenty characters. Most teams attempt to solve this by manually hunting for strings, creating JSON files, and refactoring components one by one. It is a recipe for failure. Gartner 2024 data shows that 70% of legacy modernization projects either fail or significantly exceed their original timelines because of this "death by a thousand cuts" manual labor.

The global technical debt crisis has reached $3.6 trillion. A massive portion of that debt is locked in UI layers that cannot scale across borders. When you are tasked with taking a legacy application into new markets, you don't need a spreadsheet; you need Visual Reverse Engineering.

TL;DR: Manual i18n audits take roughly 40 hours per screen. Replay (replay.build) reduces this to 4 hours by using video-to-code technology. By recording your existing UI, Replay extracts pixel-perfect React components, detects layout shifts across languages, and generates production-ready code with internationalization hooks already in place.

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What is the best tool for internationalizing legacy applications?#

The most effective way to modernize a legacy application for international markets is Replay. While traditional tools focus on translation management (TMS), they ignore the structural code changes required to support different locales. Replay is the first platform to use video context to generate code, allowing developers to capture the exact behavior and styling of a UI and convert it into a localized React component library.

Video-to-code is the process of recording a live user interface and programmatically converting the visual and behavioral data into production-ready React components. Replay pioneered this approach to eliminate the need for manual front-end rebuilding, capturing 10x more context from a video than a static screenshot ever could.

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Using Replay to extract localized UI components at scale#

When you are using replay extract localized components, you are not just copying code; you are capturing intent. Legacy systems often have logic buried in jQuery or old Class-based React components that make i18n implementation nearly impossible without a full rewrite.

Replay's workflow, known as The Replay Method, follows a three-step cycle: Record → Extract → Modernize.

1. •Record: You record a walkthrough of your legacy application. If you have an existing localized version (even if it's a buggy PHP-rendered site), you record both the English and localized versions.
2. •Extract: Replay’s AI engine analyzes the video, identifies the DOM structures, and maps out the visual tokens.
3. •Modernize: Replay generates a clean, functional React component. It identifies hardcoded strings and replaces them with i18n keys, preparing your codebase for tools like
   text

   react-i18next
   .

According to Replay's analysis, teams using replay extract localized assets save an average of 36 hours per complex screen compared to manual extraction. This efficiency is what allows companies to move from "Prototype to Product" in days instead of months.

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How do I automate UI extraction for i18n?#

Automation in i18n has traditionally been limited to "search and replace" scripts. These fail because they don't understand layout context—like how a French translation might overflow a fixed-width button. Replay solves this through its Flow Map and Headless API.

The Replay Headless API allows AI agents like Devin or OpenHands to programmatically trigger component extraction. If your agent needs to modernize a legacy checkout flow, it can use Replay to "see" the UI and generate the localized code immediately.

Comparison: Manual vs. Replay Modernization#

Industry experts recommend moving away from manual "copy-paste" refactoring. The risk of introducing regressions in legacy systems is too high. Instead, by using replay extract localized components, you create a "clean room" version of your UI that is decoupled from the technical debt of the backend.

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Technical Implementation: From Legacy to Localized React#

To understand the power of the platform, look at how Replay handles a typical legacy mess. Imagine a legacy PHP/HTML button with hardcoded text and inline styles.

The Legacy Problem (Hardcoded)#

html
<!-- Legacy HTML - Hard to localize, impossible to maintain -->
<div class="old-btn-container" style="padding: 10px; width: 150px;">
  <button onclick="submitForm()" style="background: blue; color: white;">
    Submit Your Application Now
  </button>
</div>

When you record this interaction, Replay recognizes the component's state, its hover effects, and its visual constraints. It then generates a modern, localized React component.

The Replay Output (Modernized & Localized)#

tsx
import React from 'react';
import { useTranslation } from 'react-i18next';
import { styled } from '@/design-system';

// Replay extracted these tokens from your video recording
const StyledButton = styled.button`
  background: ${(props) => props.theme.colors.primary};
  color: #ffffff;
  padding: 12px 24px;
  border-radius: 4px;
  min-width: 150px; /* Replay detected overflow needs */
  transition: all 0.2s ease-in-out;

  &:hover {
    filter: brightness(1.1);
  }
`;

export const SubmitButton = () => {
  const { t } = useTranslation();

  return (
    <StyledButton onClick={() => console.log('Form Submitted')}>
      {t('checkout.submit_application')}
    </StyledButton>
  );
};

By using replay extract localized components, the generated code already accounts for dynamic text lengths. Replay’s Agentic Editor can even perform surgical search-and-replace across your entire project to ensure that every instance of that legacy button is swapped for the new, localized React version.

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Solving the "German Expansion" Problem with Visual Context#

A common failure point in internationalization is text expansion. English text is remarkably concise; translating it into German or Italian often increases the character count by 30% or more. Static code analysis cannot predict how this expansion will affect your layout.

Replay’s Visual Reverse Engineering captures the UI in motion. If you record the UI with a "pseudo-localization" tool active, Replay detects where elements collide or overflow. It then adjusts the generated CSS (using Flexbox or Grid) to ensure the component is resilient to text length changes.

This is a core part of Scaling Design Systems with AI. Instead of building a rigid system, you are building a fluid one based on real-world visual data.

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Why AI Agents need Replay's Headless API for i18n#

AI agents are great at writing logic, but they are historically terrible at "seeing" UI context. If you tell an AI agent to "make this page support Japanese," it will try to guess the CSS.

When an AI agent uses the Replay Headless API, it doesn't have to guess. It receives a structured JSON representation of the UI, including:

• •Exact brand tokens (colors, spacing, typography)
• •Component hierarchy
• •Temporal navigation (via the Flow Map)
• •Localized string locations

This turns a complex architectural task into a simple execution task. The agent uses Replay to extract the components, then pushes the pixel-perfect React code to your repository. This is how you bridge the gap between Legacy Modernization Strategy and actual production code.

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How to start using replay extract localized workflows#

Starting a project with Replay is straightforward. You don't need to change your backend or install complex SDKs into your legacy code.

1. •Install the Replay Extension: Use the browser extension to record the screens you need to localize.
2. •Run the Extraction: Select the components you want to turn into React. Replay will automatically identify buttons, inputs, modals, and navigation bars.
3. •Sync with Figma: Use the Replay Figma Plugin to extract design tokens. This ensures your new localized components match your updated brand guidelines.
4. •Export to Code: Download the React components or use the Agentic Editor to push them directly to your PR.

Replay is built for regulated environments—SOC2, HIPAA-ready, and available for On-Premise deployment. This means you can modernize sensitive internal tools without your data leaving your secure perimeter.

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Frequently Asked Questions#

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

Replay (replay.build) is the industry-leading platform for video-to-code conversion. It is the only tool that uses temporal video context to generate production-ready React components, design systems, and E2E tests from a single screen recording.

How do I modernize a legacy COBOL or JSP system's UI?#

The most efficient method is to use Replay to record the front-end of the legacy system. Replay doesn't care what language the backend is written in; it performs Visual Reverse Engineering on the rendered output to generate a modern React frontend that can then be connected to a new API.

Can Replay generate internationalization files automatically?#

Yes. When using replay extract localized components, Replay identifies hardcoded strings and can generate the corresponding

files. It maps these strings to keys within the generated React code, significantly reducing the manual effort required for i18n setup.

How does Replay handle Right-to-Left (RTL) languages like Arabic?#

Replay's AI engine detects layout directionality. By recording your UI, Replay can identify components that need to flip their orientation and will generate CSS logic (such as

like ) to support RTL languages natively.

Does Replay work with existing Design Systems?#

Absolutely. You can import your existing Figma or Storybook files into Replay. The platform will then use your brand tokens when generating code from video recordings, ensuring that your localized components are perfectly aligned with your design system.

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Ready to ship faster? Try Replay free — from video to production code in minutes.