User:Muchos/Snippets/How to customize link thumbnails

In article & discussion comments and on category pages, Fandom links can display a thumbnail (a little image associated to the link content). How is it made and how to customize it?

From the article wikicode
According to User:Kirkburn (June 2016), the image chosen is generally the first image on the page that satisfies these criteria:
 * Larger than 130 × 115 px (pixels) for use on category pages; larger than 200 × 100 px for the related pages module. Note: the size on the "File:" page is what counts, not how it displays on the page.
 * Used 10 times or fewer in content namespaces on the wiki.
 * One of the first 50 used on the page.
 * Not an SVG.

Kirkburn adds: The "first" image on the page is generally the one that comes first when the article's wikitext is scanned by the software, and it doesn't matter if the image has come via a template or isn't written in standard form.

Personal conclusion: we can expect to force the thumbnail choice by such codes: Not sure about how search engine algorithms will enjoy it though.

From Theme Designer
Theme Designer quickly introduced a feature named Community site image. This should be the default thumbnail if above criteria are not met. Community site image:
 * Can be .png or .jpg.
 * Its recommended size is 600 × 450 px with a minimum size of 200 × 200 px. The maximum upload size is 1 MB (megabyte).
 * The image is stored at "File:Site-community-image".

More infos on [https://community.fandom.com/f/p/4400000000003427809 "What is a 'Community site image'?" (discussion topic, August 2022)].