I did a post about this app a few days ago, but decided to follow it up with this video after a few questions came in.
LocalSend can securely send files, text, media, and Android app APKs quickly over a local network between Windows, macOS, iOS, Android, and Linux devices. An individual text message will be able to be copied straight to the clipboard on the receiving device. Optionally, media such as photos or videos can also be copied straight to a mobile device’s photo gallery.
LocalSend uses a secure communication protocol that allows devices to communicate with each other using a REST API. All data is sent securely over HTTPS, and the TLS/SSL certificate is generated on the fly on each device, ensuring maximum security.
Apart from being encrypted via SSL, the traffic does not leave your local network, and no external 3rd party services such as GDrive, DropBox or PushBullet are used. There are no adverts or trackers either.