Android
Turn On/Off Web Link Previews in Messages auf Android
Google Messages generates link previews by quietly fetching metadata from a website as soon as a URL appears in a conversation. If you send or receive a link and no preview shows up, or previews keep appearing when you would rather see plain text, the Automatic previews setting inside Messages is responsible.
This function works independently from your mobile browser. It requests the title, description and thumbnail of the linked site over your active data or Wi-Fi connection, which is why previews can be delayed on a slow connection or missing entirely when data saver mode is active.
To switch the behavior, go to Tap on Messages ➔ Tap on Google Account ➔ Tap on Messages settings ➔ Tap on General ➔ Tap on Automatic previews ➔ Enable or disable Show all previews. Turning this off stops Messages from requesting preview data for any link, not just in a single conversation.
If previews still fail to load after enabling the setting, check your mobile data or Wi-Fi connection first, since the preview depends on reaching the linked website. Disabling previews entirely is the better choice if you want to avoid Messages contacting external servers before you actually open a link.