Free Online Loudness and Sound Meter by Youlean
No, all audio data is being used locally. It has the ITU-R BS.1770-4, or dB A-Weighted mode. Analyzing from the microphone will not give you accurate SPL-Loudness values since it is limited to the hardware on which it is being used. If you want to know the exact SPL-Loudness level please use professional hardware made for that use.

https://youlean.co/online-loudness-meter/