Fast image preview in macOS context menu (right click)
On Mac it's called Quicklook &amp; is much more powerful than just a quick jpg preview, it can also preview text, pdfs, spreadsheets, audio, movies &amp; even much more specialist data types - anything there's a plugin for.

There are two simple ways...


In column view a preview will always show to the right of the selected item. [This is a pref, accessed by hitting  Cmd ⌘   J  from any open Finder window, but defaults to on]
The size of the preview is dependant on the column width.





Alternatively, from any view, just tap the Spacebar - the preview will pop out at full size [or to fit screen]. You can resize by dragging a corner, same as any window.
This usually has an 'Open With' choice at the top to go straight to the default app for that file type [circled in red].
You can change the currently viewed item by changing your selection. You don't need to be able to see behind the preview for this, you can step around using the arrow keys.
Pressing Spacebar a second time clears Quicklook.




Quicklook is also available from some other apps, such as Mail, for viewing attachments that don't auto-inline, like text files, or if the view is too small, for instance a pdf.