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In this video we'll talk about the difference

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between running our app in the dev server,

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and running it in production.

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We've already seen that, when running

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a local server with "next dev",

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every time we request a page in the browser

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it will be re-rendered by the server.

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The dev server is designed to

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help us develop our app.

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While we're working on the code

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we want any changes we make to be visible

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in the browser as soon as possible.

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That's why the dev server regenerates

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the page each time,

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based on the latest code in our project.

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But that's not how things work in production.

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Let's see how to build and run

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our app for production.

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I'll stop the dev server.

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And, if we look at the help

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for the "next" tool again,

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it provides a "build" command,

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that we can use to create an

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optimized production build.

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And also a "start" command,

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that lets us run the Next.js

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server in production mode.

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So, let's add some more scripts

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to our "package.json".

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We want "build", to run "next build".

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And then a "start" script,

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that will execute "next start".

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If we save, we can then run those

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scripts in the terminal.

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Let me maximize this panel, so

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we can see the full output.

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First, we want to execute "npm run build",

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that will generate an "optimized

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production build".

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As you can see, it's pretty quick.

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The build command prints a useful summary.

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You can see that it generated a route

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for each page in our project:

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the root path, "/about", "/reviews", and so on.

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And, if you notice, there is a little

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circle before each path.

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At the bottom, it explains that the

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circle means it's a static page.

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One that's "automatically

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rendered as static HTML".

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So, the build step generated static HTML

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files for each one of our pages.

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In fact, you can see that,

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during the build process

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it also rendered our HomePage component.

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It will have rendered all our components,

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both the pages and the layout.

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It's just that we only log

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a message in the HomePage.

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But that's how it generates the static HTML.

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Now, all these pages have been generated

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inside the ".next" folder.

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If we look under "server", and then "app",

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you can see that there are HTML

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files for all our pages:

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"about.html", "index.html", and so on.

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Let's take a quick look at "index.html".

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I'll format the document,

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it was generated as a single

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line to minimize its size.

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Anyway, you can see here that this HTML contains

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the elements rendered from our HomePage component,

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and also from the RootLayout component.

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So all our React components have been pre-rendered

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to HTML during the build process.

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This way the Next.js server can simply

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return that index.html file,

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whenever a client requests the home page.

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Don't worry about the exact structure

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of this ".next" folder.

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It's all done automatically by the "next" command.

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Now, let's see how to run our app.

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We can simply type "npm start",

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and this will launch the Next.js server.

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By default it runs on localhost on port 3000,

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just like the dev server.

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But with "next start" it's running

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in production mode.

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Let's open the home page,

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and I'll do a hard-reload, just to make

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sure the browser doesn't use the cache.

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The home page of course looks

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the same as in dev mode.

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However, if we reload the page,

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we don't see any messages printed

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to the server logs.

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So, the HomePage doesn't get

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re-rendered every time,

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like when running it in the dev server.

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As we've seen, the build step generated a static

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HTML file inside the ".next" folder,

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so the production server will simply

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return that existing file,

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which is faster than regenerating

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the page every time.

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The production server is optimized for speed.

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Let's take a look at the network requests as well.

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When we load the page from the production server,

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it should be faster than with the dev server,

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although this is a very simple page, and

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we're running everything locally,

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so it's not a particularly meaningful test.

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Now, since we're talking about

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running our app in production,

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there are actually a few different ways

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we can deploy a Next.js project.

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And it's better if you know from the start

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how you plan to make your application

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available to your users.

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What we've done in this video is run

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our app in the Node.js server.

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We did an "npm run build" first,

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and then "npm start" to launch the server,

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using our local Node.js installation.

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You could follow exactly the same

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process on a server machine,

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rather than on your local machine,

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you could then allow HTTP access to that server,

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and you'll have a website that people can visit.

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But there are easier solutions as well.

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Next.js is developed by a company called Vercel,

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that offers a cloud platform where,

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among other things,

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you can deploy your Next.js application.

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It's not the only platform that provides

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this kind of functionality.

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You can do something similar with AWS Amplify,

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Netlify, and so on.

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The advantage of these platforms is that

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you don't need to set up and maintain

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the servers yourself.

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If you want the greatest flexibility

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in terms of where you can deploy your website,

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then you can do a static HTML export.

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This lets you build your project into a folder

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containing only static HTML, JavaScript,

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and other files,

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and you can then upload that

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folder to any web server.

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But not all of the Next.js features are compatible

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with exporting your app as static HTML.

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As we'll see later in the course,

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some features require a server

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running with Node.js.

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In the first part of this course

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we'll only use static pages

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that are compatible with doing

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a static HTML export.

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I'll tell you when we start using features

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that require a Node.js runtime.

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In fact, once our app is a bit more complete,

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we'll also see how to deploy it to Vercel,

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or as a static website.

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The most important takeaway

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from this video is that

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when we run our app in dev mode

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some things work a bit differently

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from how they work in production.

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In particular, the dev server will re-render

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our pages every time we request them,

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but that's not the case in production,

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at least with static pages.