Subdomain Routing
Every tunnel gets a unique subdomain under tunnel.nullbore.com.
How it works
When you open a tunnel, NullBore assigns it a subdomain:
# Random (free tier)
nullbore open --port 3000
# → https://a7f3bc.tunnel.nullbore.com
# Named (Hobby+)
nullbore open --port 3000 --name myapp
# → https://myapp.tunnel.nullbore.com
Each subdomain gets its own TLS certificate automatically via Let's Encrypt.
Path-based fallback
Tunnels are also accessible via path-based URLs:
https://tunnel.nullbore.com/t/a7f3bc
https://tunnel.nullbore.com/t/myapp
Subdomain routing is preferred — it gives each tunnel full isolation (cookies, CORS, etc). Path-based URLs are a fallback for environments where wildcard DNS isn't configured.
Self-hosted subdomain setup
To enable subdomain routing on a self-hosted server:
- Configure a wildcard DNS record:
*.tunnel.yourdomain.com → your-server-ip - Start the server with:
--base-domain tunnel.yourdomain.com
The server automatically provisions TLS certificates for each subdomain on first request.
nullbore-server \
--host 0.0.0.0 \
--port 443 \
--base-domain tunnel.yourdomain.com \
--tls-domain tunnel.yourdomain.com \
--tls-email admin@yourdomain.com