This week on the Tech Minds YouTube channel Matthew introduces the "Cloudmarkers" plugin for SDRuno. SDRuno is the official software for the SDRplay RSP line of software defined radios, but the EXTio version also supports the RTL-SDR.
Cloudmarkers is a plugin that allows users to query the online Cloudmarkers database to determine what an unknown signal at the currently tuned frequency might be. The database is created by other Cloudmarkers users, so if you have your own information to add you can add information about particular frequencies to the database for others to query later.
In the video Matthew shows the Cloudmarkers plugin in operation and notes that the plugin can work with both SDRplay SDRs and the RTL-SDR.