I want to screenshot the active window and then preview it, to make sure I got what I wanted. I press apple+shift+3. A thumbnail toast shows up in the bottom right corner. I click on it and it is what I wanted.
It opens in the preview app, but there is no menu bar. apple+c and ctrl+c do not copy it into memory. How do I copy the image into memory?
I close the image. Then open it from the desktop. Then I can copy and paste it. Is there an easier way?
There's an inherent difficulty in getting a screenshot to both file and clipboard. The screenshot app does one or the other, not both, so to have both you must actually allow it to finish saving the file to Desktop then open it in something you can copy to clipboard from, such as Preview.
A slightly quicker method, which may at first seem counter-intuitive, is that if you select the file on the Desktop & copy it, the Finder quite cleverly copies all aspects of it & then can paste different aspects of the file, depending on where you paste to. Paste to a folder it will paste the file itself; to a web page it will paste the link to the file; to a text app it will paste the file's title; and to an image editor it will paste the image itself.
Clicking the screenshot floating thumbnail doesn't actually open it in the Preview app. It opens in a version of the QuickLook app [with extra annotation, similar but not identical to Preview]
QuickLook
You can from here click the Share icon, top right & send it to Preview.
Preview
If you want the initial floating thumbnail to go to the copy buffer, right click it before it vanishes & select Save to Clipboard.
This, however, will redirect it entirely & it will no longer save to desktop as well.
You could at this point send it straight to Preview app [which would lose it from the clipboard - there's no win/win here ;)
All of these choices are the same whether you use Cmd ⌘ Shift ⇧ 3 or Cmd ⌘ Shift ⇧ 4.
From either of these, adding Ctrl ⌃ to the keyboard shortcut will send the image directly to Clipboard rather than file [yet again an either/or decision]
Cmd ⌘ Shift ⇧ 5 has its own prefs which you can change once it opens, rather than by adding Ctrl ⌃
You could actually eliminate the floating thumbnail entirely if you wished - this also makes the save to Desktop a bit faster. You do this by using the Options menu in Cmd ⌘ Shift ⇧ 5
If this all sounds a bit confusing, it's because these commands have kind of grown organically over many years, as new features were added. Once you understand them you can see the relationship they all have to each other, especially if you think of them as being oldest to newest, 3, 4, 5.
The newest Cmd ⌘ Shift ⇧ 5 implementation has the most control over what you get from it - including fullscreen, window, selection snapshots as either stills or movies - with power comes complexity… but still has no way to send to both Clipboard & file in one shot.
After capturing the whole screen with Command ⌘+Shift ⇧+3 and opening the thumbnail appearing at the bottom right, you can copy the image to the buffer by pressing Command ⌘+C. You can then paste the image wherever appropriate with Command ⌘+V.
However, if you make any changes to the image within the window opening after clicking on the thumbnail (Quick Look window), you can not copy to the buffer either the image or the changes. With this Quick Look window, you can only copy the image to the buffer when it is pristine.
The other option is to take the screen capture directly into memory by pressing Command ⌘+Control ⌃+Shift ⇧+3. No thumbnail will appear in the bottom right. In addition to pasting it wherever you like with Command ⌘+V in that case, you can have it directly opened in a Preview window by pressing Command ⌘+N after opening Preview.
See the "Take screenshots or screen recordings on Mac" Apple Support webpage for more options and details.
