ERR_NGROK_9021: You may specify at most one of subdomain, hostname, or domain for a tunnel - ngrok documentation

What does ERR_NGROK_9021 mean?

ngrok returns ERR_NGROK_9021 with this message:

You may specify at most one of subdomain, hostname, or domain for a tunnel.

Troubleshoot ERR_NGROK_9021 with your AI agent. Connect it to the ngrok MCP server, then ask what caused the error and how to fix it.

Where can I get more help with ERR_NGROK_9021?

Email support@ngrok.com and include the error code.