Massive accepts extended user IDs that let you add targeting specifications to requests. Append a standard URL query string with routing parameters to your proxy username. You can combine routing parameters in any order.

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Standard syntax

Our proxy protocol uses - syntax to append routing parameters, which will used throughout our documentation. 
curl -x https://network.joinmassive.com:65535 \
     -U '{PROXY_USERNAME}-country-US-zipcode-10001:{API_KEY}' \
     https://cloudflare.com/cdn-cgi/trace

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Alternative syntax

The alternative syntax ? + = + & is also supported. 
curl -x https://network.joinmassive.com:65535 \
     -U '{PROXY_USERNAME}?country=US&zipcode=10001:{API_KEY}' \
     https://cloudflare.com/cdn-cgi/trace