Command modifier throughout. Edit-mode shortcuts in the browser use Command the same way the desktop app does.
What the web version covers. Core slide building, text formatting, basic layout, and object management all work. Most edit-mode shortcuts from the desktop app are supported.
Presentation delivery in the browser. PowerPoint for the web can run slideshows, but the experience differs from the desktop. Some delivery shortcuts may work differently when a presentation runs inside a browser tab rather than a dedicated full-screen window. The table above covers what is confirmed for the web version.
Browser shortcut conflicts. Cmd+W closes the browser tab; Cmd+T opens a new one. These browser behaviors take priority over any matching PowerPoint web app shortcut.
Desktop vs. web feature scope. Advanced animation timing controls, SmartArt editing, and certain layout tools are more limited in the web version. Their shortcuts may not apply.