Production build not minified

[tweeres04]

• I have searched the issues of this repository and believe that this is not a duplicate.

Expected Behavior

When I'm deploying a production build, I should have minified javascript code in order to minimize file size and maximize performance.

Current Behavior

My app.js is 529KB and not minified

Steps to Reproduce (for bugs)

1. next build
2. next start

OR

1. next build
2. next export

Context

I wanted to use next.js in order to have a lightning fast site as advertised but no minification kills that. I'm sure I'm missing something simple.

Your Environment

Tech	Version
next	4.1.1
node	8.4.0
OS	MacOS Sierra 10.12.6
browser	Chrome
etc	React and react-dom 16

[liweinan0423]

Can you confirm your NODE_ENV is set to production? I guess you may have a global environment variable NODE_ENV set and next scripts would honor the user defined ENV if there is one

[mcansh]

i thinks he's referring to

Uncaught Error: React is running in production mode, but dead code elimination has not been applied. Read how to correctly configure React for production: https://fb.me/react-perf-use-the-production-build

[tweeres04]

@liweinan0423 Yes, confirmed that NODE_ENV is production.

@mcansh Yes, I'm getting that!

[mcansh]

Looks like a 4.1.1 issue as it’s not happening in 4.1.0

[timneutkens]

Did a new release (4.1.2) can you try updating?

[mcansh]

looks good 👍

[timneutkens]

Thanks for verifying @mcansh 👌

[tweeres04]

Looks good! Thanks for your quick response @timneutkens!

[zhaihaoran]

it`s still a issue for me next@4.2.1,the same question happened on the Production enviroment, need help

[ilionic]

Confirm, getting the same on 4.2.1

[rgbkrk]

Yep, this is worth reopening. I believe React changed their strategy with 16.2.0.

[timneutkens]

@rgbkrk @ilionic will be fixed when a new version of canary is released. Also will be fixed once and for all when universal webpack lands (currently working on this).

[devmetal]

Getting same on 4.2.3

The error is:

React is running in production mode, but dead code elimination has not been applied.

[ilionic]

@devmetal should be gone in latest canary version. Although getting app.js size twice as large compared to next.js 3 Investigating..

[devmetal]

@ilionic Thank you for quick answer :) Its working! You made my day! 🥇
Working with: next@4.4.0-canary.3

[nosdoska]

I'm getting this in 4.2.3 using a custom server and routing. Trying to update to the canary version now to test.

Edit:
Is working now. I'm a little intrigued now by using a canary version. It is ready for production? Or is better to wait for a release?

[devmetal]

@dazjavier I use it for production with custom server and routing, everything is working fine. No bad experience. Maybe a little bit slower in development mode, but its not big issue, and my stack also a little bit heavy, firebase, apollo, etc so maybe that cause this. Anyway, in production is working as expected :)

[nosdoska]

@devmetal Thanks for the information. I've using it for 3 days now, and everything works great. No big performance issues for now.
Thank you.

[cernadasjuan]

I am using the 5.0.0 version, and I am getting this error again

[davecarlson]

@timneutkens can this be reopened ?

[timneutkens]

It's extremely hard to get this message with v5. The only way I'm aware of is removing the react aliases in your next.config.js.
Earlier today someone on slack said he saw the warning.
Turned out he had this in his next.config.js:

if (config.resolve.alias) {
      delete config.resolve.alias.react
      delete config.resolve.alias['react-dom']
    }

To be clear. React doesn't require minification anymore. If you're using React 16+ the React is already minified when published on npm, the message is purely to point out that there might be something wrong with the transpilation. In our case we made the choice to not minify minified code and alias to the right bundle in dev/prod automatically. This saves ~20seconds with builds for us in production. And we avoid doing unneeded work.

If you removed the aliases because you have code using react-dom/server on the client side you can upgrade to next@canary which will be released as master soon 🙏

[arunoda]

And here's that canary version: https://github.com/zeit/next.js/releases/tag/5.0.1-canary.2

[davecarlson]

@timneutkens - you are correct. I'd actually done some next.config optimisations between me posted and you posting, removing the alias lines ) - and that does fix it :)