There are a few different ways to play music, podcasts, and other audio on a Google Nest or other Assistant smart speaker. Bluetooth is the least-discoverable option, but it's an excellent way to play audio from a phone, computer, or almost anything else.

Google Assistant speakers are primarily designed to start music and playback with voice commands, like saying "play Coldplay on Spotify" or "start my workout playlist on YouTube Music." No need to reach for another phone or tablet, and you can control playback with taps, button presses, or more voice commands. Easy peasy.

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However, there aren't many music services with that level of integration -- in the United States, you're limited to just YouTube Music, Pandora, Spotify, and Deezer. There are a few more options for radio or podcast-style services, like iHeartRadio, TuneIn, and Google Podcasts, but that's still sparse.

Another playback option is Google Cast (also known as Chromecast), which allows you to stream media from some phone and tablet apps. Cast isn't perfect though. Some Android devices don't always change the volume on the Cast speaker after pressing the source's volume buttons, and phones with more aggressive power management can shut down background tasks like Cast -- usually causing media to continue playing on the speaker, but without any way to control it from the source. Cast is even worse on other platforms, like iPhone and Windows, where fewer apps support the Cast API.

If a service isn't available on the speaker itself, and if Casting isn't available or won't work, the final option for most Google speakers is Bluetooth. I've started using Bluetooth any time I want to stream music from my phone or tablets to a Google smart speaker, even if the source app or device supports Cast. It's usually faster to start, and I can reliably use the volume buttons on the source to adjust the volume. There are minor downsides -- all sounds from the source will play on the speaker, and you can't do multi-room playback over Bluetooth -- but I still tend to prefer Bluetooth playback over Cast.

Bluetooth settings in Google Home app
Opening the Bluetooth settings for a Nest Hub

The option for Bluetooth playback is a bit buried, but it does exist for all Google Assistant smart speakers. Select your speaker from the Google Home app, then navigate to Audio > Paired Bluetooth devices, and press "Enable pairing mode." The speaker will then show up in your device's Bluetooth pairing list. After that, your smart speaker appears as a device in your Bluetooth devices list, just like a pair of headphones.

Bluetooth is far from the best technology around, but it does work with just about everything. Want to play Apple Music from an iPad to a Google Nest Hub? Use Bluetooth. Want to listen to MP3 files from your computer on your Nest Mini? Use Bluetooth. Heck, you can even pair an old Windows Phone or BlackBerry to a modern Google speaker using Bluetooth.

It would be great if Google still offered 3.5 mm input jacks on all its speakers, but Bluetooth is still a great way -- if not the best way -- to play media on your Google smart speaker that can't be started from the speaker itself. The next time you're fumbling with Cast support, give it a try.