4. Mirror your entire PC display
Google didn't make a big deal about this feature, but you can actually mirror your entire PC display through Chromecast, not just your open browser tabs. Click the Castbutton in Chrome and look for the little drop-down arrow on the far right, on the same line as "Cast this tab to...". Then click Cast entire screen (experimental).
This is truly an experimental feature; it doesn't even support audio right now. Still, it could be useful for sharing photo slideshows on your local PC, or throwing PowerPoint slides onto the big screen straight from Microsoft Office.
5. Stream audio from iTunes, Windows Media Player, and other desktop programs
The experimental full-screen sharing described above is easy, but it doesn't support audio streaming, at least not yet. So what if you want to use Chromecast to play tunes from iTunes, VLC, the Spotify desktop app, or another local media player? You could install a media server software, such as Plex, which will allow you to play those files through a browser tab. But if you'd rather not install anything new, Google's own Remote DesktopWeb app can help.
Oddly enough, it's possible to open the computer you're currently using as a tab within the Remote Desktop app. Once you've set up Remote Desktop (instructions here), open the app and select your current computer from the My Computers list. The browser tab itself will show an infinite cascade of windows, as the computer is essentially mirroring itself, but your local applications will open up without issue. Just make sure to turn off the audio on your computer, or else it will play on the computer and Chromecast at the same time.
6. Check out the hidden cast settings in Chrome
Hidden within the Cast extension's Options menu, you'll find additional streaming settings that control nuts-and-bolts things like the bit rate and frame rate of casted tabs. To uncover them, right-click anywhere in the Options menu and select Inspect element. In the frame that pops up, expand the line that reads "quality == 'custom'."
On the expanded line, double-click the text that reads "display: none" and delete that text. Look down seven lines further, for another "display: none". Double-click and delete that text as well. The new options should appear on the page. (If you close the Options window, you'll have to perform these steps again.)
There's actually not much evidence that these settings work right now. You can play around with them, but adjusting things like frame rate and bit rate produced no noticeable changes for me.
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