Chrome: If you want to quickly check out a link in an article, but don’t want to commit to opening a new tab or losing your place on the current page, you’d be hard-pressed to find a better extension than CoolPreviews.
The app is very similar to previously-mentioned SwiftPreview in that it lets you hover over any link and hold down the shift key to see a small preview of the page, but it outshines SwiftPreview by letting you scroll within the preview pane, and even click links without ever actually opening the page. You will need to access the extension’s settings screen to enable the hotkey option, otherwise you’ll see annoying magnifying glasses next to every link you hover over, but it’s a change you’ll only need to make once.
Google recently killed its Instant Preview feature that let you glance at webpages linked in search results without opening them, but CoolPreviews more than makes up for its absence. If you’re a Firefox user, there’s an extension available by the same name from a different developer that incorporates similar features, plus several others.