If you register (pair) multiple Bluetooth earphones on your smartphone and connect them at the same time, you might be able to enjoy listening to music at the same time, or you might be able to listen to the same song wirelessly with two people. It seems that there are not many people. In fact, you can register as many Bluetooth earphones on your smartphone/computer as you have to scroll through the screen, and since they are wired or wireless, it seems possible.
Choose the environment whether you can output sound to two Bluetooth earphones with one smartphone In conclusion, it is possible to output sound to two Bluetooth earphones with one smartphone, but choose the environment. The Bluetooth standard supports simultaneous standby (multipoint) with multiple devices, but there are very few products that support the communication specification "A2DP profile" used in Hi-Fi audio, and the transmitter (smartphone, DAP) and the receiving side (Bluetooth earphone/speaker) are used as a pair in most cases. Many Bluetooth devices that are used for voice calls and are called "headsets" support multipoint. However, most of the two devices that emit sound at the same time use the HFP or HSP profile, and there are very few products that can listen to both at the same time with A2DP. Exceptions also exist. Some Jabra Bluetooth headphones (ex. Elite 85h) support A2DP multipoint, so you can listen to music at the same time by pairing two products with one smartphone. Apple's AirPods can also play music at the same time on two AirPods if you use an iPhone/iPad running iOS 13 or later, but you can't listen like that on anything other than an iPhone/iPad because it performs its own processing.
