JMeter 407 Proxy Authentication Required: Set Proxy Credentials

A message such as Unable to tunnel through proxy ... 407 Proxy Authentication Required identifies the intermediary asking for credentials. The HTTPS application request has not yet passed through an accepted CONNECT tunnel.

JMeter provides outbound proxy options together:

jmeter -n -t plan.jmx \
  -H proxy.example -P 8080 \
  -u proxy-user -a 'REPLACE_WITH_PROXY_PASSWORD'

The documented username flag is lowercase -u. Long options include --proxyHost, --proxyPort, --username and --password. The sample password is a placeholder; command arguments can be visible to other users on the machine.

For a setting owned by the test plan, HTTP Request and HTTP Request Defaults also expose proxy server, port, username and password fields. Enter the server without an http:// prefix in that hostname field. Check sampler-specific entries when a command-line change appears ineffective.

Keep an HTTP Authorization Manager entry for the destination's server authentication when the application needs one. Its URL-scoped account is a different configuration from the proxy account supplied above.

If the proxy still returns 407, inspect its advertised authentication scheme and the effective endpoint. A correct password for another proxy realm or an unsupported scheme will still be rejected. Preserve the distinction between a refused login and a connection failure, and avoid adding the proxy password as an application Authorization header.