TryUnfurl

Check How Your Links Unfurl for FREE!

See exactly how your webpage will appear when shared on social media, Slack, Discord, and messaging apps.

Try It Now →

Link Preview & URL Unfurl Guide — The Complete Developer Hub

Every link your team ships — every tweet, every Slack share, every email CTA — gets judged in half a second based on how it previews. A strong preview card earns the click. A broken card gets scrolled past. This is the complete, no-fluff hub for everything you need to know about link previews and URL unfurling: how the process works under the hood, which tags matter, what each platform requires, how to troubleshoot when a preview breaks, and how to audit previews at scale.

Everything here is written for shipping teams — engineers, marketers, SEOs, content ops — so you can get from "this link previews badly" to "fixed, verified, shipped" in the shortest possible path.

→ Test any URL on TryUnfurl · → Bulk-check 100 URLs at once

What Are Link Previews?

A link preview (also called a URL unfurl, an embed, or a rich card) is the preview tile that appears when someone pastes a URL into a social network, chat app, messaging platform, or AI assistant. The platform fetches your page, reads the metadata in the HTML <head>, and renders a compact card showing the title, description, image, and site name — so anyone scrolling can decide whether to click before they even do.

Every link preview is built from a small set of ingredients:

When any piece is missing or malformed, the preview breaks. And because platforms cache URL unfurl results — sometimes for days — a broken card stays broken long after you've deployed a fix unless you force a re-scrape.

The URL Unfurl Process Explained

Every social network and chat app runs roughly the same pipeline the moment a URL shows up:

  1. User pastes a URL into a post, message, or channel.
  2. Platform crawler fetches the page with a bot user-agent (Slackbot, Discordbot, facebookexternalhit, LinkedInBot, Twitterbot, WhatsApp, and so on).
  3. Server responds with HTML, containing the metadata tags in <head>.
  4. Platform parses the metadata, using its own priority order (Twitter prefers Twitter Card tags; LinkedIn ignores them entirely; Slack reads OG first).
  5. Preview card is rendered using the extracted title, description, and image.
  6. The preview is cached so the next share of the same URL doesn't re-hit your server.

The one thing nearly every platform has in common: they don't execute JavaScript. If your site relies on client-side rendering, your Open Graph tags must be in the initial HTML response. How link previews work covers the technical details in depth.

Platform-Specific Requirements at a Glance

Every platform renders URL unfurl cards slightly differently. Here's what matters most:

Platform Priority tags Image minimum Cache-clear mechanism
Facebook / Meta Open Graph 1200×630px Sharing Debugger
LinkedIn Open Graph 1200×627px Post Inspector
Twitter / X Twitter Cards → OG fallback 1200×628px Card Validator
Slack Open Graph ~800×800px for large cards Re-share the link
Discord Open Graph No strict minimum Query-string cache-buster (?v=2)
iMessage Open Graph + Apple-specific 1200×630px Delete and re-send
WhatsApp Open Graph ~300×200px Cache-buster query string
Microsoft Teams Open Graph 1200×630px Re-send / clear client cache
Telegram Open Graph 800×800px Re-share or use /debug

See our per-platform guides (Facebook, LinkedIn, Slack, Discord, iMessage, WhatsApp, Teams, Telegram) for the exact rules and fix workflows.

Common Unfurling Issues and Solutions

The same failure patterns show up in nearly every URL unfurl audit:

Full symptom-based diagnosis lives in the link preview troubleshooting guide, and the 7 root causes of broken previews goes deeper on each pattern.

Advanced Optimization Techniques

Once the basics are solid, these are the levers that separate a correct preview from a preview that actually earns clicks:

Testing and Validation Tools

Testing URL unfurl previews before you share is the single highest-leverage habit a shipping team can adopt. The tools fall into two buckets:

Compare the tools side-by-side or jump straight to the testing checklist.

Checklist: Optimize Your Link Previews

Before your next big share, run through this:

Guides in This Documentation

Core Concepts

Metadata References

Testing & Tools

Troubleshooting

Platform-Specific Guides

Developer Resources

Start Testing Now

You can audit your first URL in under 30 seconds.

→ Paste a URL into TryUnfurl · → Bulk-check up to 100 URLs

For more information, visit “What is Unfurling?”, our complete guide to link previewing on the internet and social media.