Test an HTTP Proxy with curl

Use a bounded curl test to inspect proxy connectivity, HTTPS tunneling, response status, and bypass rules without altering your device's global proxy.

Replace 127.0.0.1:8080 with an endpoint from your service or the HTTP proxy list and run this against a harmless HTTPS destination:

curl --noproxy '' --proxy http://127.0.0.1:8080 --connect-timeout 5 --max-time 15 --verbose https://example.com/

The loopback address means a listener on your own machine. This command selects it explicitly, clears curl's bypass list for the call, allows five seconds for connection setup and fifteen seconds overall. It leaves browser and system proxy settings alone.

Use the actual curl executable if your shell aliases curl to another program; curl --version identifies the build. If the listener itself requires TLS, use its documented proxy scheme.

Read four results, not one green light

  1. Connected to the selected proxy: the address and port are reachable.
  2. CONNECT accepted: the proxy opened a tunnel to the HTTPS destination.
  3. Destination certificate verified: TLS completed with the expected trust checks.
  4. Destination response received: inspect its status and content for the result your application needs.

A destination 403 or 429 can follow a working tunnel. curl can also exit successfully after receiving an HTTP error response, so record both the response status and curl's error result. A TCP connection or CONNECT success alone is insufficient.

A compact result for repeated comparisons

On a Unix-like shell, discard the body and print the tunnel status, destination status, peer and elapsed time:

curl --noproxy '' --proxy http://127.0.0.1:8080 --connect-timeout 5 --max-time 15 --silent --show-error --output /dev/null --write-out 'http=%{http_code} connect=%{http_connect} peer=%{remote_ip} total=%{time_total}\n' https://example.com/

http_connect describes the tunnel response; http_code describes the final HTTP response. remote_ip is curl's connection peer, not an independent measurement of the proxy's exit address. Replace /dev/null on other systems or keep the response body.

If the result fails, locate the failed setup or transfer step and compare the same destination directly where that route is allowed:

curl --noproxy '*' --connect-timeout 5 --max-time 15 --verbose https://example.com/

--noproxy '*' bypasses proxies. Failure at certificate verification on both routes points toward a shared trust problem; a direct success paired with a rejected CONNECT points toward proxy authentication or policy. Review verbose output before sharing it, since it can contain identifying information.

Save the endpoint, target and timestamp with the outcome. This establishes what worked for that request; future availability, privacy and performance under load require separate evidence.

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