How to use a proxy: system, browser, phone and code

Originally published on proxymint.

How to use a proxy on Windows, macOS, iPhone, Android, Chrome, Firefox, curl and Python: what the details mean, where they go, and how to check it works.

TL;DR

• Using a proxy takes four steps. Read the host, port, username, password and protocol, pick where the proxy applies, enter the details there, then verify the exit IP and country.
• Scope decides what leaks. A system setting covers only apps that read it, a browser setting covers one browser, and a script covers exactly the requests it sends.
• Credentials are the usual failure. The Windows dialog and Android's Wi-Fi proxy have no password field, and Chrome and Firefox have no field for a SOCKS5 login.
• Keep the proxy URL on http:// or socks5h://. HTTPS sites still run end to end through a CONNECT tunnel; https:// to the proxy is a different feature.

Key takeaways

• Pick the smallest scope that does the job. Set the proxy in the script or app when you can, and use the system setting only when every app must follow it.
• Verify the country, not just the IP. Compare an IP echo call with and without the proxy, and treat a changed IP in the wrong country as a failed setup.
• Use socks5h for SOCKS. It sends the hostname to the proxy, so DNS lookups do not leave from the local network.
• Read a 407 as a login problem. The proxy refused the credentials and the site never saw the request, so check the username, password and encoding first.
• Match the proxy type to the target. Datacenter for lenient targets and tests, residential for targets that score IP type, static ISP for one fixed login location.

Read the full guide on proxymint, with the commands, tables and sources.