ERR_NGROK_331: You may not create an endpoint using a domain with the TLD SUFFIX

What does ERR_NGROK_331 mean?

ngrok returns ERR_NGROK_331 with this message:

You may not create an endpoint using a domain with the TLD <SUFFIX>. This TLD is not reachable over the public internet. Failed to create an endpoint with the domain <DOMAIN>.

Troubleshoot ERR_NGROK_331 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_331?

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