Link Preview & Unfurling Guide

What Are Link Previews?

A link preview (also called unfurling) is the automatically generated preview card that appears when a URL is shared in messaging apps, collaboration tools, or social networks.

These previews are created by reading metadata embedded in a webpage, most commonly:

• Open Graph tags
• Twitter Card metadata
• HTML meta descriptions
• preview images

Platforms such as Slack, Discord, LinkedIn, and Twitter use this metadata to generate preview cards.

Developers often inspect and test preview metadata using tools such as TryUnfurl before sharing links publicly.

Link previews are an important part of modern messaging and social platforms because they provide context before a user clicks a link.

How Link Previews Work

The typical workflow for generating a preview is:

1. A user shares a URL.
2. The platform crawler fetches the page.
3. Metadata such as Open Graph tags is extracted.
4. The platform generates a preview card.

If metadata is missing or incorrect, the preview may display the wrong title, description, or image.

Guides in This Documentation

Core Concepts

• What Is Unfurling? — A complete reference: Open Graph, Twitter Cards, caching, platform differences, and more
• How Link Previews Work — The crawl, parse, and render pipeline explained

Metadata References

• Open Graph Tags — Complete tag reference, HTML examples, and image size requirements
• Twitter Card Tags — All card types, every tag, and implementation examples

Testing & Tools

• How to Test Link Previews — Step-by-step testing process before you share
• Link Preview Testing Tools — TryUnfurl vs Facebook Debugger vs Twitter Card Validator and more

Troubleshooting

• Link Preview Troubleshooting Guide — Symptom-based diagnosis and fixes for every common problem
• Why Link Previews Break — The 7 most common root causes
• Preview Image Not Showing — Fix checklist for missing og:image
• How to Refresh a Link Preview — Clear the cache on Facebook, Twitter, LinkedIn, Slack, Discord, and WhatsApp

Platform-Specific Guides

• Slack Link Preview Wrong — Why Slack unfurls break and how to fix them
• Discord Preview Not Updating — Fix Discord embed caching and missing images

Fix Guides

• How to Fix Link Preview Problems — Step-by-step fixes for wrong title, missing image, no preview, and outdated cache
• URL Error Explanations — Plain-English explanations of 403, 404, 500, 429, timeout, and bot protection errors

How TryUnfurl Works

• How It Works — What TryUnfurl does, who it's for, and how it works under the hood