Part 7.6 — Production Builds, Webpack Comparisons & Debugging

Production is where assumptions break.

Things that worked perfectly in development suddenly fail:

• routing behaves differently

• environment variables are missing

• builds succeed but the app crashes

• performance degrades mysteriously

This post gives you the mental model to debug production React apps calmly—without blaming the build tool.

1. Production Is a Different Environment

Key differences from dev:

• code is minified

• tree-shaken

• bundled

• environment variables are baked in

• error messages are compressed

Never assume “it worked in dev” means “it works in prod.”

2. Understand the Production Build Output

With Vite:

pnpm build

This produces:

• static HTML

• hashed JS/CSS assets

• optimized chunks

Always inspect:

• output size

• chunk names

• asset count

Blind builds are dangerous builds.

3. Source Maps Are Non-Negotiable

Enable source maps for production debugging.

In vite.config.ts:

export default {
  build: {
    sourcemap: true,
  },
};

This allows:

• readable stack traces

• proper error reporting

• faster incident resolution

Without source maps, production debugging is guesswork.

4. Debugging “White Screen” Failures

Common causes:

• missing env variables

• runtime errors during boot

• incorrect base paths

• routing misconfiguration

Steps:

1. check browser console

2. check network tab

3. verify index.html loads

4. verify JS chunks load

Production debugging starts in the browser.

5. Routing Issues in Production

Single-page apps require server support.

If you see 404s on refresh:

• your server isn’t serving index.html for all routes

Fix at the hosting layer (Vercel, Netlify, Nginx).

This is not a React Router bug.

6. Environment Variables in Production

Remember:

• frontend env vars are build-time

• changes require rebuilds

• missing vars resolve to undefined

Always:

• log critical envs at startup (in dev)

• validate required envs

• fail fast if missing

Silent failures are costly.

7. Performance Debugging in Production

If performance regresses:

• check bundle size

• inspect code splitting

• look for accidental eager imports

• profile real devices

Production performance ≠ dev performance.

8. Vite vs Webpack: The Reality

You kept the Part title intentionally—but here’s the truth.

Vite:

• faster dev

• simpler config

• modern defaults

Webpack:

• mature ecosystem

• extreme customization

• slower feedback loops

For most React apps today:

• Vite is the right default

• Webpack is for legacy or special cases

Tool choice rarely fixes architectural problems.

9. When Build Tool Choice Actually Matters

Build tooling matters when:

• you ship very large apps

• you need deep customization

• you integrate unusual assets

• you debug edge production issues

For 90% of apps, clarity and discipline matter more.

10. Logging and Error Reporting

Production apps need:

• structured logging

• error reporting (Sentry, etc.)

• visibility into crashes

Console logs are not observability.

Plan this early—even if tooling comes later.

11. Reproducing Production Bugs Locally

Steps:

1. run a production build locally

2. serve it with a static server

3. reproduce behavior

4. debug with source maps

Never debug production-only issues in dev mode.

12. Build Failures Are Signals

Build warnings often point to:

• circular dependencies

• unused code

• incorrect imports

• fragile assumptions

Treat warnings as future incidents.

13. Production Mindset Shift

In production:

• safety > convenience

• clarity > cleverness

• observability > optimism

Production is unforgiving—but predictable if you prepare.

14. Summary

You now know how to:

• reason about production builds

• enable source maps safely

• debug runtime failures

• diagnose routing and env issues

• understand Vite vs Webpack trade-offs

• debug performance regressions

• adopt a production-first mindset

This completes Part 7 — Routing, Hooks, and Build Optimizations.