The title bar icon: drag a file straight out of the app

You want to send a document you're currently working on. The usual routine: switch to Finder, remember where the file lives, click your way to it, drag it into the message. Yet the file has been in front of you the entire time — open in a window. macOS accounts for this: next to the document's name in the title bar sits a small file icon (the so-called proxy icon), and it behaves just like the file itself. Grab it with the mouse and drag it anywhere you'd drag a file from Finder.

How to do it

1. Hover over the document's name in the title bar — on newer versions of macOS, the icon next to the name only appears after a brief hover.
2. Grab the icon and drag it into an in-progress email, a chat, the desktop, another Finder folder, or an app's icon in the Dock that you want to open the file in.
3. It works in the vast majority of apps that handle files: Preview, Pages, Numbers, TextEdit, Word, and many editors. In Safari, this is how you drag out the address of the open page.
4. A bonus for orientation: click the title bar name while holding Cmd — the full path to the file expands (folder, parent folder, drive), and clicking any level opens it in Finder.
5. If you want the icon visible permanently instead of only on hover, turn on the option to always show icons in window title bars under System Settings → Accessibility → Display.
6. Two useful extras: holding Option while dragging creates a copy of the file instead of moving it, and dragging the icon into another app's Save dialog jumps you straight to the same folder — making it easy to save a new file next to the one that's open.

A typical scenario

A manager is finishing up a proposal in Pages when the client writes asking her to send the current version. Instead of a trip to Finder — where she'd have to dig up the right project folder — she saves the file, hovers over the name in the title bar, grabs the icon, and drops it into her in-progress reply in Mail. The attachment is in the message within three seconds. She uses the same move when filing documents into project folders: she finishes the proposal, grabs the icon, and drags it straight into the right Finder folder — without ever opening a dialog. And when she can't remember the next day where she actually saved the proposal, Cmd+click on the title bar shows her the path instantly — faster than any Spotlight search.

What you get out of it

You skip the most common reason for switching to Finder — tracking down a file you already have open. Attaching files, moving them into folders, and opening them in another app all take a single drag of the mouse. And Cmd+click on the title bar reveals where a file actually lives any time, which anyone who saves things "somewhere in Documents" will appreciate.