Before you begin
Have the proxy host, port, protocol, username and password ready. Use a destination you are allowed to access. The example below uses the public demonstration site example.com.
Send one request
curl --proxy "http://PROXY_HOST:PROXY_PORT" \
--proxy-user "PROXY_USERNAME" \
--noproxy "" \
--connect-timeout 10 \
--max-time 30 \
https://example.com/Replace PROXY_HOST, PROXY_PORT and PROXY_USERNAME. cURL prompts for the password when only a username is supplied. Keep credentials out of shared shell history.
Check the result
A returned page shows that the client reached the destination through the configured proxy. Use the proxy checker to inspect the exit IP and reported country separately. A successful connection does not mean every target accepts that IP.
Add your application
Keep a connection timeout and a total request timeout. Start with one request, then add parsing and bounded retries after you understand failures. Continue with Python, Node.js or Playwright.