Next.js getServerSideProps: Usage, Examples, FAQs

getServerSideProps is a Next.js function for server-side rendering that fetches data on each request. Here's what you need to know:

Purpose: Renders pages with fresh, request-specific data
Best for: Real-time info, personalized content, SEO-critical pages
Drawbacks: Slower page loads, higher server load

Key points:

Only usable in page components
Runs on every request
Allows secure handling of sensitive data

When to use:

User dashboards
Live pricing pages
Location-based content

Quick comparison:

Method	Data Freshness	Performance	SEO
getServerSideProps	High	Slower	Good
getStaticProps	Low	Faster	Excellent
Client-side	High	Fast initial load	Poor

Use getServerSideProps only when you need data that must be fetched at request time. For static or infrequently changing content, consider alternatives like getStaticProps.

What is getServerSideProps?

getServerSideProps is a Next.js function that fetches data on the server for every page request. It's a key tool for creating dynamic, server-rendered pages with up-to-date information.

Definition and Use

getServerSideProps is a function you export from a page file in Next.js. It runs on the server before the page is sent to the browser, allowing you to:

Fetch data from APIs or databases
Access server-only resources
Perform operations that require sensitive information

Here's a basic example:

export async function getServerSideProps() {
  const res = await fetch('https://api.example.com/data')
  const data = await res.json()
  return { props: { data } }
}

function Page({ data }) {
  return <div>{data.title}</div>
}

export default Page

In this case, the server fetches data from an API and passes it to the Page component as props.

Comparing Data Fetching Methods

Next.js offers several ways to fetch data. Here's how getServerSideProps stacks up:

Method	When It Runs	Best For	Caching
getServerSideProps	Every request	Frequently changing data	No built-in caching
getStaticProps	Build time	Static content	Cached at build
getInitialProps	Server and client	Legacy method	No built-in caching

getServerSideProps is ideal when you need fresh data on every page load, such as for personalized content or real-time information. However, it can be slower than pre-rendered methods like getStaticProps.

"Use getServerSideProps only when you need to render a page whose data must be fetched at request time", advises the Next.js documentation.

Remember, getServerSideProps:

Runs on every page request
Can't be used in non-page files
Allows direct database or API calls without exposing secrets to the client

When to Use getServerSideProps

getServerSideProps is a powerful Next.js function, but it's not always the best choice for every situation. Let's explore when you should use it and how it compares to other data fetching methods.

Best Use Cases

Use getServerSideProps when:

You need fresh data on every request: If your page displays real-time information that changes frequently, getServerSideProps ensures users always see the latest data.
SEO is critical: For pages where search engine optimization is important, getServerSideProps allows search engines to crawl fully rendered content.
You're working with user-specific data: When displaying personalized content based on user authentication or preferences, getServerSideProps can fetch this data securely on the server.
You need to access server-only resources: If your page requires data from APIs or databases that shouldn't be exposed to the client, getServerSideProps is the way to go.

Method Comparison Table

Method	When to Use	Pros	Cons
getServerSideProps	- Real-time data - SEO-critical pages - User-specific content	- Always fresh data - Good for SEO - Secure for sensitive data	- Slower Time to First Byte (TTFB) - Higher server load
getStaticProps	- Static content - Infrequently changing data	- Fast page loads - Reduced server load	- Data can become stale - Not suitable for personalized content
Client-side fetching	- Non-SEO critical pages - Frequently changing data	- Fast initial page load - Real-time updates possible	- Poor for SEO - Initial content flash

While getServerSideProps ensures up-to-date content, it comes at the cost of longer load times. For pages where SEO isn't crucial and immediate data updates are necessary, client-side fetching might be a better option.

How to Use getServerSideProps

Basic Structure

To use getServerSideProps, export it from a page component in your Next.js application. The basic structure looks like this:

export async function getServerSideProps(context) {
  // Fetch data here
  return {
    props: {}, // Will be passed to the page component as props
  }
}

The context parameter is an object containing useful information about the request, such as params, req, res, and query.

Here's a real-world example that fetches data from the GitHub API:

export async function getServerSideProps() {
  const res = await fetch('https://api.github.com/repos/vercel/next.js')
  const repo = await res.json()
  return { props: { repo } }
}

export default function Page({ repo }) {
  return <main><p>{repo.stargazers_count}</p></main>
}

This code fetches information about the Next.js repository and displays the number of stars it has.

Output Types

getServerSideProps can return different types of output, each serving a specific purpose:

Output Type	Description	Example
props	Key-value pairs passed to the page component	`{ props: { message: "Hello" } }`
notFound	Boolean to return a 404 status	`{ notFound: true }`
redirect	Object for redirecting to another page	`{ redirect: { destination: '/', permanent: false } }`

Let's look at examples for each output type:

1. Props

export async function getServerSideProps() {
  return {
    props: { message: "Welcome to the About Page" },
  }
}

2. Not Found

export async function getServerSideProps() {
  const res = await fetch(`https://api.example.com/data`)
  const data = await res.json()
  if (!data) {
    return { notFound: true }
  }
  return { props: { data } }
}

3. Redirect

export async function getServerSideProps() {
  const userLoggedIn = false
  if (!userLoggedIn) {
    return {
      redirect: {
        destination: '/login',
        permanent: false,
      },
    }
  }
  return { props: {} }
}

getServerSideProps runs only on the server, making it suitable for handling sensitive data or server-only resources. However, it can slow down your page load times, so use it wisely.

Advanced Uses and Examples

Let's explore some advanced uses and examples in Next.js applications.

Complex Data Fetching

getServerSideProps excels at fetching data from multiple sources. Here's an example that combines data from an internal API and an external service:

export async function getServerSideProps(context) {
  const { params, req, res } = context;
  const [internalData, externalData] = await Promise.all([
    fetch(`https://api.myapp.com/data/${params.id}`).then(r => r.json()),
    fetch('https://api.github.com/repos/vercel/next.js').then(r => r.json())
  ]);

  return {
    props: {
      internalData,
      externalData
    }
  };
}

This code fetches data from both an internal API (using dynamic route parameters) and the GitHub API simultaneously, improving performance.

Handling Errors

Error handling in getServerSideProps is crucial for a smooth user experience. Here's a pattern for managing errors and redirecting users:

export async function getServerSideProps(context) {
  try {
    const data = await fetchDataFromAPI();
    return { props: { data } };
  } catch (error) {
    console.error('Error fetching data:', error);
    return {
      redirect: {
        destination: '/error',
        permanent: false
      }
    };
  }
}

This example logs the error and redirects the user to a custom error page, preventing the application from crashing.

Using Redirects and Not Found

getServerSideProps can handle various scenarios, including redirects and 404 errors. Here's an example that covers both:

export async function getServerSideProps(context) {
  const { params } = context;
  const res = await fetch(`https://api.example.com/data/${params.id}`);
  const data = await res.json();

  if (!data) {
    return { notFound: true };
  }

  if (data.redirectUrl) {
    return {
      redirect: {
        destination: data.redirectUrl,
        permanent: false
      }
    };
  }

  return { props: { data } };
}

This code checks if the requested data exists. If not, it returns a 404 status. If the data includes a redirect URL, it performs a redirect. Otherwise, it returns the fetched data as props.

"With good caching and performant fetching, you can swap out the ubiquitous SPA spinner for snappy page loads." - Dan Abramov, React Developer

Common Questions

Usage Questions

Many developers have questions about how to use getServerSideProps effectively. Here are some common queries:

Q: When should I use getServerSideProps?

A: Use getServerSideProps when you need to fetch data at request time. It's ideal for pages that require:

User-specific content (e.g., personalized dashboards)
Real-time data (e.g., live sports scores)
Frequently changing information (e.g., stock prices)

Q: How do I handle errors in getServerSideProps?

A: Error handling in getServerSideProps is crucial. Here's a pattern you can follow:

export async function getServerSideProps(context) {
  try {
    const data = await fetchData();
    return { props: { data } };
  } catch (error) {
    console.error('Error fetching data:', error);
    return {
      redirect: {
        destination: '/error',
        permanent: false
      }
    };
  }
}

This code logs the error and redirects users to an error page if data fetching fails.

Q: Can I use getServerSideProps with TypeScript?

A: Yes, you can use getServerSideProps with TypeScript. Here's how:

import { GetServerSideProps } from 'next'

export const getServerSideProps: GetServerSideProps = async (context) => {
  // Your code here
  return {
    props: {} // Will be passed to the page component as props
  }
}

Fixing Common Problems

Developers often face issues when using getServerSideProps. Here are solutions to typical problems:

Problem: Slow page loads

If your getServerSideProps function takes too long, it can lead to slow page loads. In March 2023, a Next.js developer reported a 5-second delay in their getServerSideProps function, resulting in poor user experience.

Solution: Keep your data fetching fast. If it takes longer than 2 seconds, consider:

Optimizing your data fetching
Using caching strategies
Moving some data fetching to the client-side

Problem: "window is not defined" error

This error occurs when trying to access browser-specific objects in getServerSideProps.

Solution: Remember that getServerSideProps runs on the server. Avoid using browser-only APIs like window or document. If you need these, use them in useEffect hooks or client-side components.

Problem: Unable to access external modules

Developers sometimes face the "Module not found" error when trying to use certain Node.js modules.

Solution: Ensure all Node.js and server-related code is inside getServerSideProps. For example:

export async function getServerSideProps() {
  const fs = require('fs')
  const data = fs.readFileSync('/tmp/data.txt', 'utf8')
  return { props: { data } }
}

Good Practices

Improving Speed

To make server-side rendered pages faster with getServerSideProps, consider these tips:

Implement caching: Use a caching layer like Redis to store and serve frequently accessed data. This reduces the load on your server and speeds up response times.
Optimize data fetching: Minimize the amount of data you fetch in getServerSideProps. Only retrieve what's necessary for the initial page render.
Use Incremental Static Regeneration (ISR): For pages with data that changes infrequently, ISR can provide a good balance between static generation and server-side rendering.
Leverage CDNs: Content Delivery Networks can serve static assets and pre-rendered pages quickly, reducing load times for users across different geographical locations.
Optimize database queries: Use indexes and efficient SQL queries to reduce data fetching time.

Here's an example of implementing an LRU cache in your Next.js application:

import LRU from 'lru-cache';
const ssrCache = new LRU({ max: 100, maxAge: 1000 * 60 * 60 }); // 1 hour

Keeping Data Safe

When handling sensitive data with getServerSideProps, follow these security practices:

Use React's taint APIs: Prevent sensitive data from being exposed to the client by using the experimental_taintObjectReference and experimental_taintUniqueValue functions.

Example:

import { queryDataFromDB } from './api'
import { experimental_taintObjectReference, experimental_taintUniqueValue } from 'react'

export async function getUserData() {
  const data = await queryDataFromDB()
  experimental_taintObjectReference('Do not pass the whole user object to the client', data)
  experimental_taintUniqueValue("Do not pass the user's address to the client", data, data.address)
  return data
}

Implement security headers: Add recommended security headers to your Next.js application in the next.config.mjs file:

Header	Purpose
Content-Security-Policy	Mitigates XSS attacks
Referrer-Policy	Controls HTTP Referer header information
X-Frame-Options	Prevents clickjacking attacks
X-Content-Type-Options	Prevents MIME type sniffing
Strict-Transport-Security	Enforces HTTPS usage
Permissions-Policy	Specifies allowed APIs and features

Use CSRF protection: Create a secure cookie with a short expiration date and validate CSRF tokens on the server-side to prevent Cross-Site Request Forgery attacks.
Handle authentication carefully: Implement server-side checking to determine if a user is logged in. Use a function like getSessionFromServer(req) to verify user authentication.
Keep sensitive API requests server-side: Ensure that all sensitive API requests are handled within getServerSideProps to keep them secure from client-side exposure.

Drawbacks and Limits

Common Problems

Using getServerSideProps in Next.js can lead to several issues that developers should be aware of:

Slower Page Transitions: Moving between pages can be noticeably slower with server-side rendering (SSR), especially for data-heavy pages. This can impact user experience, particularly on slower networks.
Performance Bottlenecks: SSR can put a strain on server resources, potentially causing slowdowns during high traffic periods. This is because the server must render the page for each request, unlike static generation.
Complex Caching: Implementing effective caching strategies for SSR pages is more challenging than for client-side rendered (CSR) or statically generated pages.
Higher Server Costs: SSR often requires more powerful servers to maintain good performance, which can increase operational expenses.
Limited Interactivity: SSR pages may have reduced interactivity compared to CSR, which can be a drawback for highly dynamic web applications.
Larger Attack Surface: SSR sites typically have more potential vulnerabilities than CSR sites, making them potentially harder to secure.

To mitigate these issues:

Use SSR selectively, only for pages that truly need real-time data.
Implement efficient caching strategies to reduce server load.
Optimize server-side code to minimize rendering time.
Consider using Incremental Static Regeneration (ISR) for pages with less frequent data updates.

Effects on Speed

Server-side rendering with getServerSideProps can significantly impact your application's speed:

Aspect	Impact on Speed
Initial Load Time	Can be slower due to server-side processing
Time to First Byte (TTFB)	Often higher compared to static generation
Subsequent Page Loads	Generally slower than client-side navigation
Server Response Time	Increases with complex data fetching or heavy logic
Network Latency	More pronounced effect due to server round-trips

To optimize speed when using getServerSideProps:

Minimize data fetching: Only retrieve essential data for initial render.
Implement efficient database queries: Use indexing and query optimization techniques.
Utilize connection pooling: This can significantly reduce database connection overhead.
Consider edge computing: Deploy your Next.js application closer to your users to reduce latency.

Using with TypeScript

TypeScript adds static typing to Next.js projects, helping catch errors early and improve code quality. Here's how to use getServerSideProps with TypeScript:

TypeScript Types

Next.js provides the GetServerSideProps type for use with getServerSideProps:

import { GetServerSideProps } from 'next';

export const getServerSideProps: GetServerSideProps = async (context) => {
  // Your server-side logic here
  return {
    props: {
      // Your props here
    }
  };
};

To ensure type safety for props, use the generic type parameter:

interface Props {
  data: string;
}

export const getServerSideProps: GetServerSideProps<Props> = async () => {
  const data = await fetchData();
  return {
    props: {
      data
    }
  };
};

TypeScript Example

Here's a practical example of using getServerSideProps with TypeScript:

import { GetServerSideProps } from 'next';

interface User {
  id: number;
  name: string;
  email: string;
}

interface Props {
  user: User;
}

export default function UserPage({ user }: Props) {
  return (
    <div>
      <h1>{user.name}</h1>
      <p>Email: {user.email}</p>
    </div>
  );
}

export const getServerSideProps: GetServerSideProps<Props> = async (context) => {
  const userId = context.params?.id as string;
  const res = await fetch(`https://api.example.com/users/${userId}`);
  const user: User = await res.json();

  if (!user) {
    return {
      notFound: true,
    };
  }

  return {
    props: {
      user,
    },
  };
};

This example fetches user data server-side and passes it to the page component with proper typing.

To simplify prop typing, use the InferGetServerSidePropsType utility:

import { InferGetServerSidePropsType } from 'next';

export default function UserPage({ user }: InferGetServerSidePropsType<typeof getServerSideProps>) {
  // Component logic here
}

This approach reduces code duplication and ensures type consistency between server-side data fetching and client-side rendering.

Wrap-up

Key Points Review

Let's recap the main takeaways for using getServerSideProps effectively:

Server-side rendering: getServerSideProps fetches data on each request, making it ideal for pages that need up-to-date information.
Use cases: It's best for pages with personalized content, real-time data, or information that changes often.
Performance trade-offs: While it ensures fresh data, it can increase server load and response times compared to static content.
SEO benefits: Pages using getServerSideProps can have better SEO for dynamic content compared to client-side rendering.
TypeScript integration: You can use TypeScript with getServerSideProps for improved type safety in your Next.js projects.

Closing Thoughts

When deciding to use getServerSideProps, consider these points:

Selective use: Apply it only to pages that truly need real-time or personalized data.
Caching strategies: Implement caching to improve performance where possible.
Alternative methods: For less frequently updated content, consider Static Site Generation (SSG) or Incremental Static Regeneration (ISR).
Error handling: Implement robust error handling to enhance user experience and troubleshoot issues quickly.

More Information

Next.js Docs

For the most up-to-date and accurate information on getServerSideProps, check out the official Next.js documentation:

These pages offer in-depth explanations, syntax details, and usage guidelines straight from the Next.js team.

Guides and Tutorials

To deepen your understanding of getServerSideProps, explore these community resources:

Resource	Description	Key Topics
Next.js Blog	Official Next.js blog with updates and tutorials	New features, best practices
Vercel Guides	Practical guides from Next.js creators	Deployment, optimization
Lee Robinson's Blog	Insights from Next.js Developer Advocate	Real-world use cases, tips

These resources offer practical insights and real-world examples to help you make the most of getServerSideProps in your Next.js projects.

FAQs

When should I use getServerSideProps?

Use getServerSideProps when you need to render a page with data that can only be known at request time. This includes:

Personalized user data
Authorization headers
Geolocation information

For example, an e-commerce site might use getServerSideProps to fetch and display region-specific pricing or inventory levels based on the user's location.

How to handle errors in getServerSideProps?

Error handling in getServerSideProps involves:

Creating a custom 500 error page
Returning an object in the catch block

Here's a basic error handling structure:

export async function getServerSideProps(context) {
  try {
    // Your data fetching logic here
    return { props: { /* your data */ } }
  } catch (error) {
    console.error('Error:', error)
    return { props: {} } // Always return an object
  }
}

During development, Next.js will show the error overlay instead of the 500 page for easier debugging.

Where can I use getServerSideProps?

getServerSideProps can only be used in page components. It's not available in regular components or API routes. Place it in files under the pages directory, such as:

pages/index.js
pages/products/[id].js
pages/dashboard.js

Where should I use getServerSideProps?

Use getServerSideProps in scenarios where you need server-side rendering with fresh data for each request. Common use cases include:

Use Case	Example
User Authentication	Fetching user-specific data after login
Dynamic Pricing	Displaying real-time prices based on market conditions
Geolocation Services	Showing content tailored to the user's location
Real-time Data	Displaying up-to-the-minute sports scores or stock prices