Errors

HTTP responses

Status	Meaning	What to check
407 Proxy Authentication Required	Authentication failed	Credentials; targeting option syntax; bandwidth balance; account status
400 Bad Request	Malformed request, or an https:// URL sent as a plain forward	Use CONNECT for HTTPS (any normal HTTP client does)
502 Bad Gateway	No exit matched your targeting, or the exit could not be reached	Loosen the target and retry
504 Gateway Timeout	The exit did not answer within the handshake budget	Retry - the next connection gets a different exit

SOCKS5

Failures surface as the standard reply codes: an auth sub-negotiation failure for anything a 407 would cover, 0x04 (host unreachable) when nothing matched your target or the dial timed out, and 0x01/0x05 for exit-side connection failures.

Notes

• 407 is always an account or username problem, never the pool. The most common surprise: a typo in a targeting option (country-de instead of cc-de) fails auth by design.
• Retries are cheap. Rotating exits means a retry is a different household. Scraping clients should treat 502/504 as “retry with the next IP”.
• A small fraction of residential exits accept a connection and then deliver nothing. If a connection establishes but stalls, drop it and retry rather than waiting it out.