Exposing localhost to the internet via tunneling (using ngrok): HTTP error 400: bad request; invalid hostname

Troubleshot this issue with ngrok. In the words of inconshrevable, some applications get angry when they see a different host header than expected.

Running the following command should fix the problem:

ngrok http [port] -host-header="localhost:[port]"

Depending on the version, you may also want to try:

ngrok http [port] --host-header="localhost:[port]"