This page uses the development build of react: in-depth guide.

Austrian Development:

Austrian Development is an impressive JavaScript library for building user interfaces. This library is applied both in development and production environments. The following message a developer comes across as he works with React, “This page is using the development build of React.” In reality, such a message can reach the browser console when developers are coding. This type of message may look innocuous on the surface, but its connotations are rather meaningful to the performance and efficiency of your application.

Let’s dig into what this message means, how it may affect your application, and how to fix it so you can start optimizing your React applications for production. We also discuss some questions that arise concerning the development build of React.

What is “Development Build” in React?

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React comes in two different builds of its library: the dev build and the prod build. Both of them are optimized toward a particular goal.

Development Build:

The development build of React is built, specifically with a rich developer experience in mind. Additional features include things like

• Detailed error messages: In the development mode, React provides detailed more informative error messages, important for debugging.
• Warns and guidelines: The React code issues warnings in the development mode for common mistakes or anti-patterns in React code. Such warnings help developers avoid certain mistakes.
• More logging to the console: There’s more logging to the console, which illuminates details about the ins and outs of how React works, and this is crucial in enhancing debugging and performance.
• Debugging support: There’s added code in the development build to simplify the debugging of React applications.

But, whilst they are incredibly valuable features to a developer, there is a performance cost. The development build is so much slower than the production build and can cause performance degradation in a live, production scenario.

Production Build:

The production build of React is optimized for performance. It is minified to remove unnecessary whitespace, comments, and debug information; it results in a much smaller file size. Plus:
These development-specific warnings and error messages are removed in the build for production.

The React runtime is optimized for speed:

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Some modern JavaScript engine optimizations can be taken advantage of by the production build to load and run more efficaciously at runtime. Developers will often use Webpack, CRA, or some other build tool to make a production build by minifying and bundling the code.

 What does the “development build” warning have to do with this?

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If you see the message “This page is using the development build of React.”, it’s usually because your application is running the dev build of React rather than its optimized prod version. It may be due to any of these reasons:

• Wrong build configuration: You most likely have your application not correctly set up to run the production build of React. You test your application more locally on development build. During the deployment prep, you must be sure that the production build is being generated.
• It’s not set up correctly optimized: If you’re working with a build tool like Create React App, Webpack, or Vite, you’re probably going to have an issue with the configuration that it’s failing to generate the production build.
• Not using production environment variables: Without the production environment variables, many build tools rely on environment variables to tell when you are in the development process versus when you have deployed it to a production environment. This would cause React to load the development build even into a production environment without proper environment variables.

Example:

In CRA, you run the following commands in your terminal to build a production-ready version of your app:

bash
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npm run build
The command above creates a build/ directory containing the production build of your application. As long as you deploy this directory on your server, React will run in production mode; however, if you use a local server that doesn’t contain the production build, you might still see a message printed by the development build.

Why avoid using the development build in production?

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The development build of React is so precious in development that it is not friendly to the production environments. That are many significant reasons behind this fact:

1. Performance Issues:

This makes the development build slower than the production build because this one is doing all the extra checks and logs error messages. Such operations in addition could make this build poorly performed especially where applications are complex or big. In the case of a production environment, good user experience would be defined by fast loading and smooth interaction, and the development build can degrade that experience.

2. Larger File Sizes:

That’s why the development build is so slow. It just carries more information for debugging, logging, and error handling.
This makes the loading times much longer and consumes much more bandwidth. For mobile device users or people on a slow internet connection, they are huge issues.

3. Extra Debugging Information:

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The development build includes very verbose logging and very verbose error messages to help developers track down problems in their applications. In a production environment, such logs are so unnecessary and could potentially leak some sensitive information or the implementational details that would be exploited by some users.

4. High Memory Use

The build of React that is meant for development comes with extra code used to detect prop types and validate components. It does use up extra memory and also contributes to degrading an application’s performance, too, especially in a mobile or resource-constrained environment.

How Do You Know You’re Using the Production Build of React:

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The fact that a React app is utilizing the production build of React can be determined through:

1. Building Your Application for Production:

Be sure to use the production build command. For example, in Create React App (CRA), this is performed with:
“`
bash
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npm run build
“`
This generates an optimized build for production in the build/ directory.

2. React Version in Production:

Once you have built your application to production, ensure the version of React used is the production version. You can verify this in the developers tool of your browser at the console. It should not read “development build.” If that is the case, something went wrong with the build process, and this is what mentions this.

3. Set NODE_ENV to “production”:

NODE_ENV should be set to the ‘production’ environment variable when running the build. You can do this as follows, in a Webpack-based setup:

bash
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NODE_ENV=production webpack –config webpack.config.js
This ensures you use the production build of React and possibly its optimizations like minification.

4. Minify and Optimize Your Code:

Ensure your build process includes minifying and optimizing your JavaScript. For example, for Webpack, there is TerserPlugin integrated into the code to remove unused code and minify your application.

FAQs on React Development Build:

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1. What happens if I ignore the development build warning?

If you disregard that alert and keep on using the development build in your production, chances are that your application will be running with very slow loads, and interactions will not be responsive. This can make the experience less friendly to users, and thus may cause increased bounce rates or disappoint users.

2. What is the proper way to tell if my React app is in a production build?

To verify whether your application indeed runs the production build of React, you open a developer tool in your browser (F12), open your console, and look for messages. In case you get messages on the “development build,” then you are still running on the development version of React.

3. Can I switch from dev mode to production mode without rere-building React?

No, you can’t switch from development to production mode. You need to rebuild your app for this reason: React relies on optimizations that take place at build time. In this way, you can statically ensure that the right version of React is used. Once you have created your production build, it will start using the optimized production version of React.

4. Can I deploy my React app without using the script npm run build?

Technically you may deploy the not optimized version of your app, though strongly not recommended. Applying the development build in production will the performance and user experience of your app severely.

5. What else should I optimize to apply to React in production?

Besides the production build of React, there are more performance optimizations for production React apps.

• Code splitting: You can leverage React’s lazy loading to chop up your application into much more manageable and much smaller pieces.
• Server-side rendering (SSR): You can render your React app to speed up the very first load of a page.
• Static site generation (SSG): If your app doesn’t frequently change, you could pre-render your app at build time and serve that as static files.
• Image optimization: Compress images and serve them in modern formats like WebP.

Conclusion:

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Using a development build of React in production will have serious performance pitfalls, including slow load times, high memory usage, and unwanted console logging. There are thus ample reasons to ensure that your application is built with the production version of React to leverage optimizations to make for the best possible experience in user interaction.
That way, by following the series of steps outlined here, you’ll know that your application uses a production build and won’t succumb to all the common pitfalls associated with development builds. Optimizing your React app into production will give you faster, more efficient applications that you could better serve users.