WooThemes

Daan Kortenbach

Enables a preview mode for widgets. In preview mode, widgets are only visible for admins.

WP Widget Preview

Enables a preview mode for widgets. In preview mode, widgets are only visible for admins.

filipstepanov

This is simple and lightweight plugin for WP. It works similar to Facebook’s url preview and it’s very easy to use.
Plugin uses free LinkPreview API web-service at http://www.linkpreview.net and retrieves basic link SEO data.
Additionally, in dashboard plugin settings you can avoid using API and scrap the link information directly from local web server using CURL or file_get_contents.
All the link info retrieved can be stored in cache to avoid possible performance impact on high traffic websites. Aside other plugin’s settings in dashboard, there is Cache time value where you can specify in minutes how long to keep URL’s information for future use.
Both LTR and RTL content environments are supported.
Two different plugin features are at your disposal, tooltips and shortcode:
Tooltip
Tooltip feature hooks on content load and scans for possible link matches. Each link matched is being modified with additional attributes, so when you hover them, popup is shown.
It’s using plugin’s JavaScript and WordPress Ajax to deliver content on demand.
Shortcode
When used through shortcodes it works the same way, just no hover needed but static content like Facebook’s URL preview will be shown.
Shortcode usage example:
[link_preview]http://…[/link_preview]

Phee's LinkPreview

Preview basic SEO link info before clicking it

WP Widget Preview vs Phee's LinkPreview