You give the proxy service the public IP address of your server or office. From then on, any request from that address is accepted. It is convenient for tools that cannot send a proxy login, and it breaks the moment your own address changes, which home and mobile connections do often.
PiratProxies plans sign in with a username and password and do not use an allowlist. If a program only takes a host and a port with no login, a small local forwarder solves it: it listens without a login on your own machine and adds the login on the way out.
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