1. The Exit IP
curl https://api.ipify.org; echo # your own address curl -x http://USER:[email protected]:PORT https://api.ipify.org; echo # through the proxy
The second line should print the proxy's address. Run it a few times: a static proxy returns the same address every time.
2. Who Owns It, and Where It Appears
curl -x http://USER:[email protected]:PORT https://ipinfo.io/json
org shows the network the address belongs to. For an ISP proxy, expect a consumer internet provider there, not a hosting company. country and region are what most sites use for location. If something looks wrong, compare with a second lookup service before concluding anything: location databases differ.
3. DNS Leaks
With an HTTP proxy, the proxy looks up the site's address, so your own DNS resolver never sees which sites you visit. With SOCKS5, it depends on the URL scheme:
curl -x socks5://USER:[email protected]:SPORT https://example.com # your machine looks up example.com curl -x socks5h://USER:[email protected]:SPORT https://example.com # the proxy looks it up
Use socks5h (or your library's “remote DNS” option) to keep lookups at the proxy.
4. WebRTC in Browsers
A browser set to use a proxy can still reveal your own address through WebRTC, which video calls use to connect directly. Open a WebRTC leak test page in the browser that uses the proxy. If it shows your own public address, turn off non-proxied WebRTC: in Chrome and Edge, the WebRtcIPHandling policy set to disable_non_proxied_udp, or an extension that does the same; in Firefox, set media.peerconnection.ice.proxy_only to true in about:config.
5. Speed
Time the connection stages, then a 100 MB download from a public test file:
P=http://USER:[email protected]:PORT curl -o /dev/null -s -x $P https://example.com \ -w "proxy %{time_connect}s tls %{time_appconnect}s total %{time_total}s\n" curl -o /dev/null -s -x $P https://proof.ovh.net/files/100Mb.dat \ -w "%{speed_download} bytes/s\n"
Compare with the same commands without -x. The proxy adds a hop, so some extra time is normal; the distance between you, the proxy and the site matters most.
If a Test Fails
How to fix proxy errors goes through each error message, and ISP vs residential vs datacenter proxies explains what the ownership lookup tells sites about an address.