# Mastodon Open Graph

## Test and debug your Open Graph tags for Mastodon

### Mastodon Specs

|     |     |
| --- | --- |
| Image size | 1200x675px |
| Aspect ratio | 1.78:1 |
| Max file size | 5 MB |
| Formats | image/jpeg, image/png, image/webp, image/gif |
| User-Agent | Mastodon/4.3.0 (http.rb/5.2.0; +https://mastodon.social/) |

[Official docs](https://docs.joinmastodon.org/entities/PreviewCard/)

Mastodon generates preview cards when a URL is shared in a status, pulling data from Open Graph meta tags and oEmbed endpoints. Unlike centralized platforms, every Mastodon instance fetches and caches preview data independently, so your link can look different across the fediverse.

This guide covers how Mastodon’s per-instance crawling works, which tags it reads, image sizing rules, cache behavior, and the most common issues that prevent preview cards from appearing.

## What links look like on Mastodon

### The difference Open Graph tags make when sharing a link.

#### Without Open Graph

This site doesn't have Open Graph

opengraphplus.com

Mastodon Open Graph

Oh

#### With Open Graph

Sites with Open Graph look like this

opengraphplus.com

Mastodon Open Graph

Nice!

### Debug Mastodon Open Graph tags

Enter your site's URL to see how it looks on Mastodon.