Websdr started a 3 year journey/obsession into SDR for me. Proceed with caution.
FWIW KiwiSDR has a map of accessible receivers similar to websdr.
One cool thing you can do is TDoA analysis with multiple receivers to attempt to locate the origin of a signal (click extensions->TDoA in the radio GUI)
A tip. If you want to hook up QSSTV or Fldigi to a web SDR, you
can do with paprefs+pulseaudio under Linux (enable the loopback
device in paprefs) and with sndiod under OpenBSD at /etc/rc.conf.local:
OpenWebRX[1] is a similar open-source sdr frontend, KiwiSDR is based on a slightly older version before it was picked up by a new maintainer. It's really nice being able to use the digital protocol decoding baked-in to it. Usually in the VHF ham band you can park it on the default "PACKET" bookmark and look at all the APRS traffic going around, and if the person running it has added the VHF/UHF buisness bands in that particular area the POCSAG decoder works great. Same for the digi protocols like FT8 et al. on the HF ham bands.
There's also another online directory[2] of mostly all available KiwiSDR, OpenWebRX, and WebSDR receivers with a cool map view.
I ran an OpenWebRX node for a good while before taking it down with the intention of upgrading it to an SDR with a wider bandwidth and a few multi-band antennas for better performance, might get around to finishing that up now.
websdr is software connected to SDR hardware - often cheap/somewhat cheap SDR USB dongles originally meant for DVB-t TV - that uses them to receive much much more of the spectrum than intended. Used by all kind of hobbyists to listen to radio, HAM radio, CB, plane beacons, baloons and many more.
This site lists multiple websites that uses such software exposed as web service, so you can listen to chosen frequency in a lab in Germany, or in US, and see what they can receive. Just using web browser, courtesy of many people around the globe.
FWIW KiwiSDR has a map of accessible receivers similar to websdr.
One cool thing you can do is TDoA analysis with multiple receivers to attempt to locate the origin of a signal (click extensions->TDoA in the radio GUI)
http://kiwisdr.com/public/