Link previews

Link previews are available in some places in Nextcloud. There are 3 types of link preview:

The ones for links that are supported by a reference provider
- Without custom reference widget (uses a default generic style, image + title + description)
- With custom reference widget (implemented by the app which supports the link)
Default ones from OpenGraph information. This is the fallback for every unsupported link

Where do they appear?

The link previews provided by the Nextcloud reference system appear in the following places:

Text (and Collectives pages, Notes, Deck card comments, Files comments etc…)
- Directly in the document content, next to the links
- Only one link preview per paragraph is rendered
- Custom widgets can be rendered
Talk
- In the messages
- Only one link preview per message is rendered
- Custom widgets can be rendered
Nextcloud Office
- In the document content when hovering on links
- Custom widgets are not rendered

How does it work?

The Nextcloud frontend asks the server to resolve the links via an API request. A rich object is returned as a response and is used by the frontend to render the preview.

The apps can optionally register a custom reference widget to render a specific rich object type (on the links it supports). Therefore the apps have complete freedom over how some previews look like.

Known link preview providers

Collectives: Links to Collective pages
Tables: Links to tables
Deck: Links to boards, cards and comments
Talk: Links to conversations
GitHub integration: Links to GitHub issues, pull requests, comments and repositories
GitLab integration: Links to Gitlab issues, merge requests, comments and repositories
Zammad integration: Links to Zammad tickets
Reddit integration: Links to subreddits, publications and comments
Mastodon integration: Links to members and toots
The Movie Database integration: Links to people, movies and series
OpenStreetMap integration: Location links from OpenStreetMap, Google maps, Bing maps, Here maps and Duckduckgo maps
Giphy integration: Links to GIFs
Notion integration: Links to Notion documents
Peertube integration: Links to videos