Dynamic OG images in NextJS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What does this Next.js dynamic OG image component render?

Consider this Next.js API route that generates a dynamic OG image using the @vercel/og library. What will be the output image's text content if the query parameter ?title=Hello%20World is passed?

NextJS

import { ImageResponse } from '@vercel/og';

export const runtime = 'edge';

export async function GET(request) {
  const { searchParams } = new URL(request.url);
  const title = searchParams.get('title') || 'Default Title';

  return new ImageResponse(
    (
      <div style={{
        backgroundColor: 'black',
        height: '100%',
        width: '100%',
        display: 'flex',
        justifyContent: 'center',
        alignItems: 'center',
        color: 'white',
        fontSize: 48,
        fontWeight: 'bold',
      }}>
        {title}
      </div>
    ),
    {
      width: 1200,
      height: 630,
    }
  );
}

A An image with white background and black text 'Hello World' centered

B An image with black background and white text 'title' centered

C An image with black background and white text 'Default Title' centered

D An image with black background and white text 'Hello World' centered

💡 Hint

Look at how the title variable is set and used inside the JSX.

The component reads the title query parameter from the URL. If it exists, it uses that text inside the image. Since the query parameter is ?title=Hello%20World, the text rendered is 'Hello World'. The background is black and text is white as per the styles.

📝 Syntax

intermediate

Which option fixes the syntax error in this dynamic OG image code?

This Next.js API route code snippet has a syntax error. Which option fixes it correctly?

NextJS

import { ImageResponse } from '@vercel/og';

export const runtime = 'edge';

export async function GET(request) {
  const { searchParams } = new URL(request.url);
  const title = searchParams.get('title') || 'Default Title'

  return new ImageResponse(
    <div style={{ backgroundColor: 'black' }}>{title}</div>,
    {
      width: 1200,
      height: 630,
    }
  );
}

A Add a semicolon after the title assignment line

B Change <div> to <div></div> with closing tag

C Wrap the JSX in parentheses after return

D Add async keyword before function GET

💡 Hint

JSX expressions returned directly must be wrapped in parentheses if multiline.

The JSX passed to ImageResponse is multiline and must be wrapped in parentheses to avoid syntax errors. Adding a semicolon or changing tags does not fix this syntax issue. The function is already async.

🔧 Debug

advanced

Why does this dynamic OG image API route return a 500 error?

Given this Next.js API route code for dynamic OG images, why does it return a 500 Internal Server Error when accessed?

NextJS

import { ImageResponse } from '@vercel/og';

export const runtime = 'edge';

export async function GET(request) {
  const { searchParams } = new URL(request.url);
  const title = searchParams.get('title');

  return new ImageResponse(
    <div style={{ backgroundColor: 'black', color: 'white' }}>
      {title.toUpperCase()}
    </div>,
    {
      width: 1200,
      height: 630,
    }
  );
}

A ImageResponse requires a string, but JSX is passed instead

B title is null if query param missing, so calling toUpperCase() causes error

C Missing await before new ImageResponse causes runtime error

D The runtime 'edge' is not supported for this API route

💡 Hint

Consider what happens if the title query parameter is not provided.

If title is null (no query parameter), calling toUpperCase() on null causes a runtime error, leading to a 500 response. The other options are incorrect because JSX is valid for ImageResponse, no await is needed, and 'edge' runtime is supported.

❓ state_output

advanced

What is the width and height of the generated OG image?

In this Next.js dynamic OG image API route, what are the dimensions of the generated image?

NextJS

import { ImageResponse } from '@vercel/og';

export const runtime = 'edge';

export async function GET(request) {
  return new ImageResponse(
    <div style={{ backgroundColor: 'blue', color: 'white' }}>Test</div>,
    {
      width: 1200,
      height: 630,
    }
  );
}

A Width 1200px and height 630px

B Width 630px and height 1200px

C Width 1024px and height 768px

D Width 800px and height 600px

💡 Hint

Check the options object passed to ImageResponse.

The image dimensions are explicitly set to width 1200 and height 630 in the options object passed to ImageResponse. This is a common size for OG images.

🧠 Conceptual

expert

Which statement about Next.js dynamic OG images is true?

Choose the correct statement about generating dynamic OG images in Next.js using the @vercel/og package and edge runtime.

A Using the edge runtime allows generating OG images on-demand with low latency at the CDN edge

B Dynamic OG images can only be generated at build time, not on-demand at request time

C The <code>ImageResponse</code> component requires a React class component as input

D Dynamic OG images cannot include custom fonts or styles

💡 Hint

Think about the benefits of edge runtime and @vercel/og for image generation.

Next.js dynamic OG images with @vercel/og and edge runtime generate images on-demand at request time with low latency near users. They support React functional components, custom fonts, and styles. Build-time only generation is false.