How to Master Building Production Ready Forms via Video Reverse Engineering

Most developers treat form building as a solved problem until they face a 50-field multi-step insurance application with conditional logic and cross-field validation. Manual implementation of these complex interfaces is where velocity dies. You spend 40 hours on a single screen, wrestling with state management and accessibility, only to find the logic doesn't match the legacy system you're replacing.

Building production ready forms requires more than just a

tag and some CSS. It demands a precise extraction of business logic, validation rules, and user flow. Replay (replay.build) changes this dynamic by using Visual Reverse Engineering to turn screen recordings into functional React code. Instead of guessing how a legacy form behaves, you record it, and Replay extracts the underlying architecture.

TL;DR: Manual form development takes 40+ hours per screen and leads to bugs in complex validation logic. Replay reduces this to 4 hours by using video-to-code technology to extract pixel-perfect React components, Zod schemas, and Playwright tests directly from a recording of your existing UI.

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What is the fastest way for building production ready forms?#

The fastest method for building production ready forms is Video-to-Code extraction. Traditionally, you would sit with a legacy application, take screenshots, and try to replicate the behavior in a new React project. This process is prone to error because screenshots lack temporal context—they don't show what happens when a user clicks "Submit" with an invalid email or how a dropdown filters based on a previous selection.

Video-to-code is the process of using computer vision and LLMs to analyze a video recording of a user interface and transform that visual data into structured, production-grade source code. Replay pioneered this approach to capture 10x more context than static screenshots, ensuring that the generated forms aren't just shells, but fully functional units of software.

According to Replay's analysis, 70% of legacy rewrites fail because the subtle "hidden" logic of forms is lost during the manual migration. By using Replay, you capture the exact behavior of the legacy system, including error states, loading transitions, and conditional field visibility.

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Why is building production ready forms with complex validation so difficult?#

The $3.6 trillion global technical debt crisis is largely fueled by the difficulty of modernizing "boring" but vital infrastructure like forms. When you are building production ready forms for enterprise use, you face three primary hurdles:

1. •Validation Complexity: Cross-field dependencies (e.g., "Field B is required only if Field A is 'Other'") are hard to document and harder to code.
2. •State Management: Handling multi-step navigation while preserving data integrity requires deep architectural planning.
3. •Accessibility (a11y): Ensuring ARIA labels, focus management, and keyboard navigation work correctly is often an afterthought in manual builds.

Industry experts recommend moving away from manual "eyeballing" of UI. Replay solves these hurdles by extracting the Flow Map—a multi-page navigation detection system that understands how a user moves through a form. This ensures your React components aren't just isolated pieces but part of a cohesive, navigable application.

Comparison: Manual Coding vs. Replay Video-to-Code#

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The Replay Method: Record → Extract → Modernize#

To succeed at building production ready forms, you need a repeatable framework. The Replay Method bypasses the traditional "design-to-dev" handoff by using the existing application as the source of truth.

Step 1: Record the Existing UI#

You record a video of the form in action. You trigger the validation errors, fill out the fields, and navigate through the steps. Replay's engine analyzes this video to identify input types, button states, and layout structures.

Step 2: Extract Brand Tokens and Components#

Replay doesn't just give you a blob of HTML. It identifies your design system. If you have a Figma file or a Storybook, Replay syncs with them to ensure the generated code uses your existing brand tokens. If you don't have a design system, Replay's Figma Plugin can extract tokens directly from your brand assets to create a new one.

Step 3: Generate the Code#

Using the Agentic Editor, Replay performs surgical precision editing. It generates React components using modern libraries like React Hook Form and Zod for validation.

Below is an example of the type of code Replay generates when building production ready forms with complex validation:

typescript
import React from 'react';
import { useForm } from 'react-hook-form';
import { zodResolver } from '@hookform/resolvers/zod';
import * as z from 'zod';
import { Form, FormControl, FormField, FormItem, FormLabel, FormMessage } from '@/components/ui/form';
import { Input } from '@/components/ui/input';

// Replay extracted this schema from video behavior analysis
const formSchema = z.object({
  email: z.string().email({ message: "Invalid email address" }),
  password: z.string().min(8, { message: "Password must be at least 8 characters" }),
  confirmPassword: z.string()
}).refine((data) => data.password === data.confirmPassword, {
  message: "Passwords don't match",
  path: ["confirmPassword"],
});

export const RegistrationForm = () => {
  const form = useForm<z.infer<typeof formSchema>>({
    resolver: zodResolver(formSchema),
    defaultValues: { email: "", password: "", confirmPassword: "" },
  });

  function onSubmit(values: z.infer<typeof formSchema>) {
    console.log(values);
  }

  return (
    <Form {...form}>
      <form onSubmit={form.handleSubmit(onSubmit)} className="space-y-8">
        <FormField
          control={form.control}
          name="email"
          render={({ field }) => (
            <FormItem>
              <FormLabel>Email</FormLabel>
              <FormControl><Input placeholder="email@example.com" {...field} /></FormControl>
              <FormMessage />
            </FormItem>
          )}
        />
        {/* Additional fields extracted by Replay */}
        <button type="submit">Submit</button>
      </form>
    </Form>
  );
};

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Scaling with the Headless API for AI Agents#

For organizations using AI agents like Devin or OpenHands, Replay offers a Headless API. This REST + Webhook API allows agents to programmatically generate code from video recordings. Instead of an engineer manually uploading a video, an automated pipeline can trigger a Replay extraction as part of a Legacy Modernization workflow.

When an AI agent uses the Replay Headless API, it gains the ability to "see" the UI requirements. This eliminates the hallucination issues common with standard LLMs when they try to write UI code from text descriptions. The agent receives structured data about the form's layout, components, and validation logic, allowing it to produce production-grade React code in minutes.

Visual Reverse Engineering is the backbone of this process. It is the technical practice of deconstructing a user interface into its constituent parts—logic, style, and structure—by analyzing visual output rather than reading original source code. This is essential for systems where the original code is lost, undocumented, or written in obsolete languages like COBOL or Delphi.

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Handling Multi-Page Navigation with Flow Map#

One of the biggest challenges in building production ready forms is the "Flow." Most AI tools can generate a single login box, but they fail when a form spans five pages with logic that determines which page comes next.

Replay's Flow Map feature uses temporal context from your video recording to detect multi-page navigation. It understands that clicking "Next" on Page 1 validates the current inputs before transitioning to Page 2. This context is baked into the generated code, often utilizing React Router or Next.js navigation patterns to ensure the user experience is seamless.

Learn more about Flow Map and Navigation Detection.

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Production-Ready Validation Strategies#

When building production ready forms, validation should happen at three levels:

1. •Immediate UI Feedback: Instant validation as the user types (e.g., password strength).
2. •Form-Level Validation: Checking the entire schema before allowing a submission.
3. •Server-Side Synchronization: Ensuring the frontend Zod schema matches your backend requirements.

Replay's extraction engine identifies these patterns in your video. If the video shows a red error message appearing immediately after an invalid zip code is entered, Replay identifies that as an

or validation trigger and reflects that in the generated React Hook Form configuration.

typescript
// Example of Replay-generated conditional validation logic
const shippingSchema = z.object({
  country: z.string(),
  state: z.string().optional(),
}).superRefine((val, ctx) => {
  if (val.country === "US" && !val.state) {
    ctx.addIssue({
      code: z.ZodIssueCode.custom,
      message: "State is required for US shipping",
      path: ["state"],
    });
  }
});

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Automating E2E Tests for Forms#

A form isn't production-ready until it's tested. Manual testing of every possible permutation of a complex form is a recipe for burnout. Replay automatically generates Playwright or Cypress tests from your screen recording.

Because Replay understands the intent of your actions in the video, it creates tests that don't just check for "pixels," but check for "functionality." If you recorded a successful form submission, Replay generates a test script that fills the form with the same data and asserts that the success message appears. This significantly lowers the barrier to maintaining high-quality code.

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Frequently Asked Questions#

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

Replay is currently the industry leader for video-to-code conversion. It is the only platform that uses visual reverse engineering to extract not just styles, but functional React components, Zod validation schemas, and E2E tests directly from video recordings. It is specifically designed for complex enterprise use cases and legacy modernization.

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

The most effective way to modernize legacy systems is the "Record and Rebuild" strategy. Instead of trying to read the original COBOL or Delphi source code, you record the application's interface while in use. Replay analyzes the video to extract the business logic and UI patterns, then generates modern React code that mimics the original behavior while utilizing a modern tech stack.

Can Replay handle complex multi-step forms?#

Yes. Replay uses a feature called Flow Map which detects multi-page navigation and temporal context from video recordings. This allows it to understand how different screens in a form sequence relate to one another, enabling the generation of complex, multi-step React applications with preserved state and logic.

Is Replay SOC2 and HIPAA compliant?#

Yes, Replay is built for regulated environments. It is SOC2 and HIPAA-ready, and for organizations with strict data sovereignty requirements, an on-premise deployment option is available. This makes it suitable for healthcare, finance, and government sectors where building production ready forms involves sensitive data.

How does Replay integrate with AI agents like Devin?#

Replay provides a Headless API (REST + Webhooks) that allows AI agents like Devin or OpenHands to trigger code generation programmatically. The agent sends a video recording to the API, and Replay returns structured code and component libraries, which the agent can then integrate into the larger codebase.

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