Link Preview API - What It Does & How It Helps

Description: Intelligently extracts and returns metadata (title, description, image) from any web page to create rich link previews.

What this page is about

This page explains the link preview API that powers rich tooltips and link cards throughout our application. Whether you're a developer building link preview features, a content creator wanting to understand how previews work, or just curious about the magic behind those helpful link cards, this guide breaks it down in plain language.

What Does This Actually Do?

Think of this like a smart librarian who can instantly tell you what any book (web page) is about just by looking at its cover and first few pages. When you give this API a web address, it visits that page, reads the important information like the title, description, and main image, then gives you a neat summary card.

It's like how social media platforms show you a preview when you paste a link - our API does the same thing, turning plain URLs into informative cards with titles, descriptions, and images.

Why Do We Need This?

For Users

Rich Link Experience: See what a link is about before clicking it
Visual Context: Images and descriptions help decide if content is relevant
Faster Navigation: Preview content saves time and improves browsing efficiency
Safety: Know what you're clicking before visiting external sites

For Content Creators

Better Engagement: Rich previews encourage more clicks on shared content
Professional Appearance: Links look polished and trustworthy
Content Discovery: Helps users find and share interesting content
Social Media Optimization: Ensures content looks good when shared

For Developers

Enhanced UX: Easy integration of rich link previews in any interface
Metadata Extraction: Automatic parsing of Open Graph, Twitter Cards, and standard meta tags
Error Handling: Robust fallbacks when pages don't load or lack metadata
Performance: Fast caching and optimized metadata extraction

How It Works (The Simple Version)

API Details

Endpoint

GET /api/link-preview?url={target_url}

Request Parameters

Parameter	Type	Required	Description	Example
`url`	string	Yes	The URL to extract metadata from	`https://example.com`

Request Examples

# External website
GET /api/link-preview?url=https://github.com/microsoft/vscode

# Internal link
GET /api/link-preview?url=/about

# Social media post
GET /api/link-preview?url=https://twitter.com/username/status/123

Response Format

{
  "title": "Visual Studio Code - Code Editing. Redefined",
  "description": "Visual Studio Code is a lightweight but powerful source code editor which runs on your desktop and is available for Windows, macOS and Linux.",
  "image": "https://code.visualstudio.com/assets/images/code-stable.png",
  "url": "https://github.com/microsoft/vscode"
}

Response Fields

Field	Type	Description	Notes
`title`	string	Page title extracted from `<title>` tag	May be empty if not found
`description`	string	Page description from meta tags	Uses multiple fallback sources
`image`	string	Main image URL from Open Graph or other meta tags	Converted to absolute URL
`url`	string	The original URL that was requested	Useful for tracking

Different Ways This Gets Used

Automatic Link Previews

Most link previews happen automatically when users hover over links:

// Automatically triggered on hover
<Link onMouseEnter={fetchPreview} href="/some-link">
  Hover for preview
</Link>

Manual Preview Generation

Developers can manually fetch previews for any URL:

const fetchLinkPreview = async (url) => {
  const response = await fetch(
    `/api/link-preview?url=${encodeURIComponent(url)}`
  );
  const metadata = await response.json();
  return metadata;
};

Batch Preview Processing

For processing multiple links at once:

const urls = ['https://site1.com', 'https://site2.com'];
const previews = await Promise.all(urls.map((url) => fetchLinkPreview(url)));

Metadata Sources Supported

The API intelligently extracts metadata from multiple sources in order of preference:

Open Graph Tags (Preferred)

<meta property="og:title" content="Page Title" />
<meta property="og:description" content="Page description" />
<meta property="og:image" content="https://example.com/image.jpg" />

Twitter Cards

<meta name="twitter:title" content="Page Title" />
<meta name="twitter:description" content="Page description" />
<meta name="twitter:image" content="https://example.com/image.jpg" />

Standard Meta Tags

<title>Page Title</title>
<meta name="description" content="Page description" />
<meta name="image" content="https://example.com/image.jpg" />

Schema.org Microdata

<meta itemprop="name" content="Page Title" />
<meta itemprop="description" content="Page description" />
<meta itemprop="image" content="https://example.com/image.jpg" />

When Things Go Wrong

Common Issues

🔗 "Preview not loading for internal links"

Internal links (starting with /) are automatically resolved to full URLs
Check that NEXT_PUBLIC_APP_URL environment variable is set correctly
Verify the internal page exists and is accessible

🌐 "External website preview fails"

Some websites block automated requests or require specific user agents
Check if the target site has robots.txt restrictions
Verify the URL is publicly accessible (not behind authentication)

🖼️ "Image not showing in preview"

Images must be absolute URLs (automatically converted by API)
Some sites restrict hotlinking of images
Check if the image URL returns proper image content-type

⚠️ "Getting 'URL is required' error"

Ensure the url parameter is included in the request
URL must be properly encoded, especially if it contains special characters
Use encodeURIComponent() when building requests in JavaScript

Error Response Format

{
  "error": "Failed to fetch link preview",
  "details": "HTTP 404: Not Found"
}

Getting Help

For Users: If link previews aren't working, try refreshing the page
For Developers: Check browser console for detailed error messages and network requests
For Content Creators: Ensure your pages have proper Open Graph meta tags for better previews

Performance Considerations

Performance Metrics

Average Response Time: 800ms - 1.5s (depending on target site)
Cache TTL: No built-in caching (consider implementing for frequently accessed URLs)
Timeout: 10 seconds for external requests
User Agent: Mozilla/5.0 (compatible; IdlingApp-LinkPreview/1.0)

Optimization Tips

// Debounce preview requests to avoid excessive API calls
const debouncedPreview = debounce(fetchLinkPreview, 300);

// Cache results client-side to avoid repeat requests
const previewCache = new Map();
const getCachedPreview = (url) => {
  if (previewCache.has(url)) {
    return previewCache.get(url);
  }
  const preview = fetchLinkPreview(url);
  previewCache.set(url, preview);
  return preview;
};

Security & Privacy

Request Safety

User Agent Identification: All requests identify as IdlingApp-LinkPreview
No Cookies Sent: Preview requests don't include user session cookies
External Request Limits: Built-in timeout protection prevents hanging requests
Error Boundaries: Failed requests don't expose internal system information

Privacy Considerations

Server-Side Fetching: Your IP address visits the target site, not the user's
No Tracking: The API doesn't store or log requested URLs
Data Temporary: Metadata is only returned, not permanently stored
HTTPS Preferred: Works with both HTTP and HTTPS, but HTTPS is recommended

Development & Testing

Local Testing

# Test external URL
curl "http://localhost:3000/api/link-preview?url=https://github.com"

# Test internal URL
curl "http://localhost:3000/api/link-preview?url=/about"

# Test error handling
curl "http://localhost:3000/api/link-preview?url=invalid-url"

Integration Testing

// Test suite example
describe('Link Preview API', () => {
  test('extracts metadata from valid URL', async () => {
    const response = await fetch('/api/link-preview?url=https://example.com');
    const data = await response.json();

    expect(data.title).toBeDefined();
    expect(data.url).toBe('https://example.com');
  });

  test('handles invalid URLs gracefully', async () => {
    const response = await fetch('/api/link-preview');
    expect(response.status).toBe(400);
  });
});

Configuration Options

Environment Variables

NEXT_PUBLIC_APP_URL: Base URL for resolving internal links (required)

Last updated: 2024-01-15 | API Version: 1.0 | Source: /src/app/api/link-preview/route.ts

What this page is about​

What Does This Actually Do?​

Why Do We Need This?​

For Users​

For Content Creators​

For Developers​

How It Works (The Simple Version)​

API Details​

Endpoint​

Request Parameters​

Request Examples​

Response Format​

Response Fields​

Different Ways This Gets Used​

Automatic Link Previews​

Manual Preview Generation​

Batch Preview Processing​

Metadata Sources Supported​

Open Graph Tags (Preferred)​

Twitter Cards​

Standard Meta Tags​

Schema.org Microdata​

When Things Go Wrong​

Common Issues​

Error Response Format​

Getting Help​

Performance Considerations​

Performance Metrics​

Optimization Tips​

Security & Privacy​

Request Safety​

Privacy Considerations​

Development & Testing​

Local Testing​

Integration Testing​

Configuration Options​

Environment Variables​