Chromecast Audio was a streaming adapter that allowed users to stream music from their devices to their stereo systems or speakers. It had a 3.5 mm jack for the stereo audio cable, which doubled as an optical for users wanting to keep their audio digital-only and had a USB charging port.
Once they connected their devices to Chromecast Audio, users could select music, radio streams, or podcasts with their favorite app. They only had to press the cast button within the app and listen to their music on the paired output device.
Chromecast Audio lacked the HDMI port that its video alternative had - the Chromecast TV streaming stick. Some versions of it are still available and supported by Google - Chromecast (3rd generation) and Chromecast with Google TV.
The official reason Google provided for discontinuing the Audio line was that they already had many products for users to enjoy their music and podcasts. They informed customers the Chromecast Audio would still be supported but no longer manufactured.
A clear sign something was happening was the more than 50% discount on the device in the US – from $35 to $15. It lasted for more than three months, from Black Friday 2018 till the end of February 2019, and was evidence Google was trying to clear their stock.
Google’s decision was easy to understand considering how technology was moving towards the era of smart speakers. The first Google smart speaker, Google Home, came out in 2016 and was soon followed by a series of better-sounding (Home Max) and more affordable (Home Mini) versions.
Ever since, Google has been putting a lot of effort into developing and popularizing the series, even rebranding it as Google Nest in 2019.