Use Case

Link Preview Services

Q: How do I build a link preview service like Slack's unfurl?

Intercept pasted URLs in your app, call the Screenshotly API with the URL and a small viewport (e.g. 1200x630), then display the resulting thumbnail alongside the page title and description extracted via Open Graph tags.

Q: What image size is best for link previews?

1200x630 pixels (1.91:1 ratio) is the universal standard used by Facebook, Twitter, Slack, and Discord. Use JPEG at 80% quality for fast loading. For higher-density displays, capture at 2x and resize.

Q: How do I cache link preview images efficiently?

Cache by URL hash with a TTL of 24-72 hours. Serve cached images from a CDN. Implement stale-while-revalidate to refresh previews in the background without blocking user requests.

Q: Can I generate link previews in real time?

For user-facing inline previews, pre-generate and cache rather than calling the API in real time. Average capture takes 2-5 seconds, which is too slow for inline display. Queue captures asynchronously and show a placeholder until ready.

Build link preview services for messaging apps, social platforms, and content aggregators. Generate rich previews for any URL.

Overview

When users paste a link in Slack, Discord, or any modern chat app, they expect a rich preview. Building this unfurl functionality requires reliably rendering any URL and extracting a meaningful visual. Screenshotly handles the hard parts.

Our API captures any URL consistently, regardless of JavaScript complexity, authentication walls, or slow loading. You get a clean image that represents the page content. Combined with metadata extraction (which you'd handle separately), you have everything needed for a complete link preview.

The challenge with link previews is handling edge cases. What about single-page apps? Paywalled content? Sites that block rendering? Screenshotly handles millions of URLs daily, so we've encountered and solved these edge cases. Your preview service inherits that reliability.

Key Benefits

Build link preview features

Generate rich URL cards

Support messaging apps

Create content aggregators

Results You Can Expect

< 2s

preview generation

99.9%

URL compatibility

Scalable

to millions of previews

How It Works

Receive URL from user input (paste, share, webhook)

Check cache for existing preview of this URL

Call Screenshotly API to generate fresh preview image

Extract page metadata (title, description) via separate parsing

Cache and serve the complete preview card

Code Example

// Generate link preview
const response = await fetch('https://api.screenshotly.app/screenshot', {
  method: 'POST',
  headers: {
    'Authorization': 'Bearer YOUR_API_KEY',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    url: 'https://example.com/article',
    device: 'desktop',
    format: 'jpeg',
    quality: 80,
  }),
});

Frequently Asked Questions

How do I build a link preview service like Slack's unfurl?

Intercept pasted URLs in your app, call the Screenshotly API with the URL and a small viewport (e.g. 1200x630), then display the resulting thumbnail alongside the page title and description extracted via Open Graph tags.

What image size is best for link previews?

1200x630 pixels (1.91:1 ratio) is the universal standard used by Facebook, Twitter, Slack, and Discord. Use JPEG at 80% quality for fast loading. For higher-density displays, capture at 2x and resize.

How do I cache link preview images efficiently?

Cache by URL hash with a TTL of 24-72 hours. Serve cached images from a CDN. Implement stale-while-revalidate to refresh previews in the background without blocking user requests.

Can I generate link previews in real time?

For user-facing inline previews, pre-generate and cache rather than calling the API in real time. Average capture takes 2-5 seconds, which is too slow for inline display. Queue captures asynchronously and show a placeholder until ready.

Want a step-by-step walkthrough?

Read: Link Preview Generation Guide →

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