Hi jPendragon, I don't know whether anyone has created a similar add-on for Firefox 57+.

WebExtensions can retrieve pages in the background and can inject that content into the current page (assuming the page doesn't forbid it), so I think it's possible to create a similar preview extension. If there is an extension for Chrome that does it, perhaps the developer can adapt it for Firefox.

Could you mention the name(s) of the Chrome extension(s) you would use for this?

Maybe you'd like to give this a try :

https://addons.mozilla.org/en-US/firefox/addon/simple-link-preview/reviews/

I don't use chrome but when I googled hover preview links in chrome, I discovered ezLinkPreview & I believe there are others. The available hover preview addons just died & were not replaced when FF57 obliterated them. There has to be a way for them to be reintroduced so that their irreplaceable functionality is not permanently gone & this determined lack is not a prominent feature of FF.

That 'ezLinkPreview ' is not available on the Mozilla Add-ons page - only the extension I gave you a link to.

I saw some of the reviews and think it might be worth a try .....

I tried it & it definitely helps but doesn't work on everything. Emails with links are not able to be accessed w/o clicking on them & perhaps elsewhere. I'm still exploring it to see its applicability. I certainly appreciate your response & its timeliness. Thanks.

Please pass this on to the powers at be and/or anyone else who might be conceivably be interested in facilitating this kind of addon for FF exists.