How to turn on Speak Selection on a Mac

Turn it on

1. Open Read & Speak settings. Choose Apple menu → System Settings, click Accessibility, then Read & Speak. On macOS 14 Sonoma and 15 Sequoia it's called Spoken Content.
2. Turn on Speak selection. Switch on Speak selection.
3. Set the options. Click the info (i) button next to it to change the keyboard shortcut, choose word and sentence highlighting, and set when the controller appears.
4. Pick a voice and speed. Back in the same pane, choose a System voice and adjust Speaking rate. Use Manage Voices in the voice menu to download Enhanced or Premium voices.
5. Try it. Select text in any app and press Option-Esc. Press it again to stop.

Settings worth changing

• Highlight content: choose Words and Sentences so you can follow along. Pick a word colour that's easy to see.
• Show controller: set it to Automatically to get pause, skip and speed controls while it reads.
• Voice: the default voices are compact. Download an Enhanced or Premium voice in Manage Voices; they sound noticeably more natural. More in natural-sounding voices on Mac.
• Shortcut: if Option-Esc clashes with something, set your own.

If it doesn't speak

• You hear a sound but no speech: nothing readable is selected, or the app doesn't expose its text. Try Edit → Speech → Start Speaking, or paste the text into TextEdit.
• Nothing at all: check the shortcut isn't taken by another app, and that your output volume and device are right.
• A PDF reads page numbers and headers: that's expected; Speak Selection reads exactly what's selected. See reading PDFs aloud.
• A scanned page or image: there's no text to select. Live Text may let you select it in Preview or Photos; otherwise you need an app with text recognition.

Source: Apple's guide.

When you'd want more than Speak Selection

Speak Selection is a good quick tool. People who listen a lot tend to want a reader window that follows along, PDFs without headers and page numbers, screenshots read aloud, their place remembered, or an audio file. That's what Aloud adds, for $19 once. Both can run side by side: Aloud's default shortcut is ⌃⌥S, so it doesn't clash with Option-Esc.