00:00:00 data fetching, the most interesting concept in Next.js.

00:00:04 There are different ways in which we can fetch content.

00:00:08 A traditional way is using a use effect.

00:00:11 For example, this is what you would do.

00:00:14 Let's say that you have a homepage where you're trying to set and fetch some albums.

00:00:19 You create a new empty use state.

00:00:22 You declare a use effect within which you declare an asynchronous fetching function.

00:00:29 Within it, you have an await fetch where you're trying to get some albums, and then you return that JSON and set it to this state.

00:00:37 Finally, going a bit down, you map over those albums and show the data.

00:00:42 But this isn't super efficient.

00:00:44 There is a better alternative to fetch, and it's happening on the server side.

00:00:49 Not only is it faster and more efficient, the code is also so much cleaner.

00:00:54 Check this out.

00:00:55 You declare a new functional component called home and immediately on top of it, you make a fetch request.

00:01:02 You check if it fails.

00:01:03 If it doesn't, you simply declare it and set its response.json to the albums variable.

00:01:10 You map over it and display the details.

00:01:13 Go ahead, pause this video and test it out.

00:01:16 You don't necessarily have to do all the styles, but you can at least try to fetch the data, map over the albums, and show each album's title.

00:01:24 If you do it, visit the website and see if it works.

00:01:28 You'll not see anything.

00:01:30 You'll have to refresh to see the result.

00:01:32 And it's not because HMR is not working.

00:01:35 but rather, HMR is caching your content.

00:01:39 In latest versions of Next.js, there is a new feature called Server Components HMR Cache that allows you to cache fetch responses in server components

00:01:51 across hot module replacement refreshes in local development.

00:01:54 What this means is you'll have faster responses and reduced costs for build API calls.

00:02:01 But now, coming back to the difference between server-side fetching versus client-side fetching, first of all, you'll notice the code difference between

00:02:09 the two strategies.

00:02:10 With server-side fetching, you've wrote fewer lines of code, which improves the DX, Developer Experience.

00:02:18 But that's not the only benefit.

00:02:20 Server-side fetching has so many more benefits, like improved initial load time.

00:02:25 As a server-side data fetching allows the page to be rendered with the data already included, it reduces the time to first contentful paint,

00:02:34 FCP.

00:02:35 In the client-side example, the user sees an empty page until the data is fetched and then rendered.

00:02:41 The second and most important benefit of server-side fetching is better SEO.

00:02:48 Search engine crawlers can more easily index content rendered on the server as the content is already provided in HTML format.

00:02:57 In contrast, client-side fetching may result in content not being visible to crawlers right away, since it first needs to be fetched and then displayed

00:03:07 on the UI, which can negatively impact your SEO.

00:03:10 Next, not only is the code shorter, but the logic is simplified.

00:03:17 Server components allow you to keep data fetching logic on the server closer to your data source.

00:03:23 This can simplify your component logic and reduce the need for use effect and use state hooks.

00:03:28 And the next benefit is not that easy to understand that first, and it is automatic request deduplication.

00:03:36 Next.js provides that automatic request deduplication when fetching data on the server, which can improve performance and reduce unnecessary API calls.

00:03:46 Basically, request deduplication makes sure that when the same data is requested multiple times at once, only one request is sent.

00:03:55 It stops duplicate requests from being made.

00:03:58 And when talking about benefits of the server-side fetching versus client-side fetching, I really can't miss on improved security.

00:04:07 Keeping API calls on the server allows you to better protect sensitive information like API keys, which should never be exposed on the client side.

00:04:17 And adding to the list of benefits, we have reduced network waterfall.

00:04:21 Client-side data fetching often leads to a network waterfall where requests are made sequentially.

00:04:27 Server-side fetching can more efficiently parallelize those requests.

00:04:32 I'll teach you how to do these parallel requests in our build and deploy project, so keep watching.

00:04:38 But this isn't just about fetching.

00:04:40 You can server render any other calls.

00:04:43 Maybe a direct database call to Prisma to get the list of posts.

00:04:47 Or even with Mongoose and MongoDB, like this.

00:04:50 That's the beauty of Next.js.

00:04:53 This is achievable because these components are React server components, which allow you to access server-related resources directly.

00:05:02 This means we can make direct database calls instead of needing to create an API and then fetch that API once again.

00:05:10 And if you're still not convinced, you can always go for client-side fetching.

00:05:15 How?

00:05:16 Just add use client to the top, bring back the use effects, the use states, and you're all set.

00:05:21 Next.js will allow you to do whatever you think is best.

00:05:24 And let's be honest, this is how we all used to use Next.js when we first transitioned over from React.

00:05:31 It only feels natural, but it is the wrong way to use Next.js.

00:05:36 And that's what made me create the whole ultimate Next.js course in the first place.

00:05:40 To teach Next.js the right way.

00:05:43 But now, take a moment to test both client-side and server-side rendering.

00:05:48 You'll notice the differences I mentioned, such as seeing the blank page initially with client-side rendering, or if you inspect its source and see that

00:05:56 nothing is there, or client-side not functioning at all if you disable JavaScript.

00:06:00 In contrast, server-side fetching will still display the results even if JavaScript is turned off in the browser.

00:06:08 But now that we know that server-side fetching is preferable, let's explore different server-side strategies that allow you to manage how and when you

00:06:18 render your content on the server-side.

00:06:20 You see, this is a crucial part of Next.js.

00:06:24 And I know that some of you might be thinking, I just want to code already.

00:06:28 But without understanding these concepts, you'll probably end up saying, I hate Next.js, it never works.

00:06:35 The truth is, it does work.

00:06:38 Just not for you.

00:06:39 You just need the right skills to make it happen.

00:06:41 That's why, even on my platform, I dedicate an entire section to breaking down these strategies before we touch a single line of code.

00:06:50 And we'll be doing the same thing in this video.

00:06:53 Trust me, it'll make your life a whole lot easier.

00:06:56 The first technique is static site generation, or SSG.

00:07:02 a technique where HTML pages are generated at build time.

00:07:07 This means that the content is created when you deploy your site, not when a user requests it.

00:07:14 It's extremely fast and can be served from a CDN, but it's not suitable for websites that need frequently updated content.

00:07:22 By default, Next.js uses a static rendering strategy.

00:07:26 Your result is cached and delivered through a CDN network.

00:07:31 Ideally, you want to use this strategy for blogs, documentation sites, or marketing pages.

00:07:37 But in many cases, you'll have to go for Incremental Static Regeneration, or ISR for short.

00:07:45 It's an extension of SSG that allows you to update static content after you've built your site.

00:07:51 This means that it'll create static pages at build time behaving like SSG, And then after some time has passed, it'll create or update those static pages

00:08:03 once again after you've deployed your site.

00:08:05 Basically, it combines the benefits of static generation with the ability to refresh or update content.

00:08:13 If you want to use ISR as a strategy, you can do this in two ways.

00:08:18 The first one is time-based revalidation.

00:08:21 You can revalidate your entire page after some time by simply exporting a variable called revalidate and set it equal to the number of seconds of when

00:08:31 you want to revalidate.

00:08:32 Isn't that crazy?

00:08:34 Expert cons revalidate and then that changes your rendering strategy.

00:08:38 Super simple.

00:08:39 And the second way is to revalidate the request after some time.

00:08:43 And that would look something like this.

00:08:45 You have a fetch and then you provide the options object with next revalidate.

00:08:51 The difference between these two is that the first approach uses the revalidate export, which is a route segment config.

00:09:00 It sets the revalidation time for the entire page to 3600 seconds, or 1 hour.

00:09:06 This means that the entire page, including all data fetches within it, will be revalidated every hour.

00:09:13 While the second approach uses the next revalidate option in the fetch function.

00:09:18 It sets the revalidation time specifically for this data fetch to 1 hour.

00:09:23 This means that only this particular data fetch will be revalidated every 3600 seconds, while other parts of the page or other data fetches,

00:09:34 if any, are not affected at all.

00:09:37 And there's also on-demand validation.

00:09:39 Instead of doing it on time, you can also revalidate using Revalidate Path and Revalidate Tag for on-demand validation of content.

00:09:50 I hope that's clear enough.

00:09:51 That's how you can use ISR.

00:09:54 It's perfect for those websites whose content changes occasionally, but still doesn't need real-time updates.

00:10:01 The next rendering strategy is Server Side Rendering, or SSR.

00:10:07 It generates the HTML for a page on the server in response to a user's request.

00:10:14 This means that the content is created dynamically for each user request, and not only for each deployment.

00:10:21 It's slower than SSG and puts more load on the server, but you'll always have up-to-date content.

00:10:28 This is ideal for highly dynamic content or pages that need real-time data.

00:10:34 Similar to what we did with ISR, you can use the same configs for SSR.

00:10:38 For time-based revalidation, instead of setting it to some random number of seconds, you simply set it to 0, telling Next.js to render the page every time

00:10:47 the user requests it.

00:10:48 And if you only want to do it for specific requests, You can use the cache no store or set the revalidate to zero there.

00:10:56 And same thing happens with the on-demand validation, like revalidate path and revalidate tag.

00:11:01 You can learn more about them in the documentation.

00:11:04 But so far, everything is super intuitive.

00:11:08 And finally, there's the partial prerendering, PPR.

00:11:12 It's a new rendering model that combines static and dynamic rendering.

00:11:17 It allows you to render a static shell of a page while streaming dynamic content.

00:11:23 The key difference with PPR is that it allows for a hybrid approach within a single page, unlike other strategies that work on a page level.

00:11:33 Here's how PPR works.

00:11:35 During build time, Next.js generates a static shell of the pages.

00:11:40 This shell includes the layout and any static parts of the page in the form of components.

00:11:46 This static shell includes placeholders for dynamic content.

00:11:51 We do it by wrapping dynamic components in a suspense tag.

00:11:55 When a user requests the page, the static shell is served immediately, and then the dynamic content is streamed in as it becomes available.

00:12:05 So what does this mean?

00:12:06 Well, with PPR, you can have static components, dynamic components, and components that are partially static and partially dynamic,

00:12:15 depending on what you need.

00:12:17 you'll actually learn about all of these strategies in action in the application you'll develop today.

00:12:23 So for now, let's keep going.

00:12:24 We're almost there and ready to start building the app.