Dynamic OG images in NextJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a Dynamic OG image in Next.js?

A Dynamic OG image is an Open Graph image generated on the fly by Next.js to show customized preview images for social media sharing, based on page content or parameters.

intermediate

Which Next.js feature helps create dynamic OG images?

Next.js API routes or server components can be used to generate dynamic OG images by rendering images on the server when requested.

beginner

Why use dynamic OG images instead of static ones?

Dynamic OG images allow personalized, up-to-date previews for each page or user, improving social sharing engagement compared to static images that are the same for all pages.

intermediate

What library can help generate images dynamically in Next.js for OG images?

Libraries like @vercel/og or Puppeteer can be used to create images dynamically by rendering HTML or React components to images on the server.

beginner

How do you set a dynamic OG image URL in Next.js page metadata?

You set the <meta property="og:image" content="URL" /> tag in the page's head, where URL points to your dynamic image API route that generates the OG image.

What does OG stand for in 'Dynamic OG images'?

A Original Graphics

B Open Graph

C Online Gallery

D Optimized GIF

OG stands for Open Graph, a protocol used to display rich previews on social media.

Which Next.js feature is commonly used to serve dynamic OG images?

A Client-side rendering

B Static generation

C API routes

D Middleware

API routes allow server-side code to generate and serve dynamic images on request.

Why are dynamic OG images better than static ones?

A They can show personalized content

B They load faster on all devices

C They use less server space

D They don't require metadata

Dynamic OG images can change based on page data, making previews more relevant.

Which library is designed by Vercel to help create OG images in Next.js?

A og-image-kit

B react-og-image

C next-og-generator

D @vercel/og

@vercel/og is a library by Vercel to generate OG images dynamically.

Where do you place the OG image URL in a Next.js page?

A In the <meta property="og:image" /> tag in the head

B Inside the main content div

C In the page's footer

D In the CSS file

The OG image URL goes in the meta tag in the head for social media to read.

Explain how you would create a dynamic OG image in Next.js for a blog post page.

Think about server-side rendering and metadata setup.

Describe why dynamic OG images improve social media sharing compared to static images.

Consider how social media previews affect clicks.

Practice

1. What is the main purpose of dynamic OG images in Next.js?

easy

A. To create custom preview images automatically based on URL data

B. To improve server response time by caching images

C. To replace all static images with animated GIFs

D. To generate CSS styles dynamically for components

Solution

1. Step 1: Understand OG images

   OG images are preview pictures shown when sharing links on social media.

2. Step 2: Role of dynamic OG images in Next.js

   Dynamic OG images let you create these previews automatically using URL parameters, making each preview unique.

3. Final Answer:

   To create custom preview images automatically based on URL data -> Option A

4. Quick Check:

   Dynamic OG images = Custom previews [OK]

Hint: Dynamic OG images create previews from URL info [OK]

Common Mistakes:

• Thinking dynamic OG images improve server speed
• Confusing OG images with CSS or animations
• Assuming all images become GIFs automatically

2. Which Next.js import is required to create a dynamic OG image?

easy

A. import { generateImage } from 'next/api';

B. import { createImage } from 'next/image';

C. import { DynamicImage } from 'next/og';

D. import { ImageResponse } from 'next/server';

Solution

1. Step 1: Identify the correct import for OG images

   Next.js provides ImageResponse from 'next/server' to build dynamic OG images.

2. Step 2: Check other options

   Other imports like createImage, DynamicImage, or generateImage do not exist or are incorrect for this purpose.

3. Final Answer:

   import { ImageResponse } from 'next/server'; -> Option D

4. Quick Check:

   ImageResponse import = import { ImageResponse } from 'next/server'; [OK]

Hint: Use ImageResponse from next/server for OG images [OK]

Common Mistakes:

• Using imports from 'next/image' instead of 'next/server'
• Assuming 'next/og' or 'next/api' provide OG image tools
• Misspelling ImageResponse or import path

3. Given this Next.js API route code snippet for dynamic OG images, what will be the output image text if the URL query is ?title=Hello?

import { ImageResponse } from 'next/server';

export const runtime = 'edge';

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

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

medium

A. An image with the text 'Default' centered

B. An image with the text 'Hello' centered

C. An image with no text displayed

D. A runtime error due to missing title parameter

Solution

1. Step 1: Extract the title from URL query

   The code gets the 'title' parameter from the URL. If missing, it defaults to 'Default'. Here, the query is '?title=Hello', so title = 'Hello'.

2. Step 2: Render the image with the title text

   The ImageResponse renders a div with the title text centered. Since title is 'Hello', the image will show 'Hello' centered.

3. Final Answer:

   An image with the text 'Hello' centered -> Option B

4. Quick Check:

   title param 'Hello' = text shown [OK]

Hint: Check URL param, fallback used only if missing [OK]

Common Mistakes:

• Assuming 'Default' shows even when title is provided
• Thinking missing text causes error
• Ignoring the URL query parameters

4. Identify the error in this Next.js dynamic OG image code snippet:

import { ImageResponse } from 'next/server';

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

  return new ImageResponse(
    (
      <div style={{ fontSize: 40 }}>
        Welcome, {name.toUpperCase()}!
      </div>
    ),
    { width: 800, height: 400 }
  );
}

medium

A. Calling toUpperCase() on null if 'name' is missing causes an error

B. ImageResponse must be imported from 'next/image' instead of 'next/server'

C. The style object cannot be used inside JSX for ImageResponse

D. The GET function must be synchronous, not async

Solution

1. Step 1: Check usage of name variable

   The code calls name.toUpperCase() without checking if name is null. If the URL has no 'name' parameter, name is null, causing a runtime error.

2. Step 2: Verify other parts

   Import from 'next/server' is correct. Style objects are allowed in JSX for ImageResponse. The GET function can be async.

3. Final Answer:

   Calling toUpperCase() on null if 'name' is missing causes an error -> Option A

4. Quick Check:

   Null check missing before toUpperCase() [OK]

Hint: Always check for null before string methods [OK]

Common Mistakes:

• Assuming name is always present
• Confusing import source for ImageResponse
• Thinking style objects are disallowed in JSX

5. You want to create a dynamic OG image in Next.js that shows a user's name and their score from URL parameters. The score should show 'N/A' if missing or zero. Which code snippet correctly implements this logic? A:

const score = searchParams.get('score') || 'N/A';
const displayScore = score === 0 ? 'N/A' : score;

B:

const score = Number(searchParams.get('score'));
const displayScore = score ?? 'N/A';

C:

const score = Number(searchParams.get('score'));
const displayScore = score > 0 ? score : 'N/A';

D:

const score = searchParams.get('score');
const displayScore = score === null || score === 0 ? 'N/A' : score;

hard

A. Option A

B. Option B

C. Option C

D. Option D

Solution

1. Step 1: Understand the requirement for score

   The score should be shown as a number if positive, otherwise 'N/A' if missing or zero.

2. Step 2: Analyze each option

   Snippet A uses string fallback and compares score === 0 but score is string, so '0' === 0 false and displays '0'.
   Snippet B converts score to number but uses ?? which only replaces null/undefined, not 0 or NaN, so displays 0 for score=0.
   Snippet C converts score to number and uses a clear check: if score > 0 show score else 'N/A'. This matches requirement perfectly.
   Snippet D compares score as string with === 0, but '0' === 0 false, so displays '0'.

3. Final Answer:

   Option C -> Option C

4. Quick Check:

   Number conversion + >0 check = Option C [OK]

Hint: Convert to number and check > 0 for score display [OK]

Common Mistakes:

• Not converting score to number before comparison
• Using nullish coalescing (??) that ignores zero
• Comparing string '0' instead of numeric zero