Method · Intermediate

Troubleshooting proxy errors: 407, 400, 402, 403, 429, 502 and timeouts

Half of proxy troubleshooting is knowing who answered: the gateway or the website. The status code and where it appears tell you, and each combination has one fix.

2 min read 5 sections Updated Published

Step 1: who answered?#

Run the failing request with curl -v. A status on the CONNECT line, before Connection established, comes from the gateway; a status after it comes from the destination. Browsers show gateway failures as ERR_TUNNEL_CONNECTION_FAILED or ERR_PROXY_CONNECTION_FAILED.

Step 2: gateway codes#

CodeProxShift meaningFix
407 invalid_credentialsUsername or password rejectedCopy the pair again; check for trailing spaces; whitelisted IP changed?
400 invalid_parameterA username parameter is unknown or malformedCheck keys and values: -cc-gb not -cc-uk, -city- without spaces, -ttl- from 1m to 24h
402 insufficient_balanceNo traffic or balance leftTop up; check the sub-user ceiling if you use one
403 blocked_destinationPort or destination not allowedPort 25, UDP and IPv6-only targets are refused by design
502 no_exit_availableNo exit matches the location right nowWiden: drop -city- or -asn-, keep -cc-; retry in a minute
502 exit_failedThe exit failed before the targetRetry once; the next connection picks another exit
504 target_timeoutThe destination did not answer in timeRetry; check the target from another network

Step 3: destination codes#

CodeLikely causeFix
403 (site page)Exit type or fingerprint rejectedResidential or mobile exit; realistic client headers; sticky session for flows
429Per-IP rate limitRotate per connection; lower per-exit rate; honour Retry-After
200 with empty dataSoft blockTreat like 403; inspect content, not status
302 to a challenge pageBot checkSlow down; real browser for that target; better exit type
5xxTarget troubleBack off; not a proxy problem

Connection-level failures#

  • ECONNRESET, Connection reset by peer mid-transfer: the household exit dropped. Retry once; on a sticky session the gateway rebinds to a new exit in the same location.
  • Idle timeouts: the gateway closes connections idle for 60 seconds. Long-polling needs a fresh connection.
  • TLS errors through the proxy: never normal. Check for a local interceptor (corporate proxy, antivirus) between you and the gateway.

Step 4: decide#

  1. Credentials or parameters wrong → fix and retry (no cost).
  2. Gateway found no exit → widen the location.
  3. Target blocks the exit type → move the target to a stronger network: datacenter → residential → mobile.
  4. Target rate-limits → rotate more and slow down; never both hammer and rotate.
  5. Target broken → wait.

Questions people ask#

Does ProxShift ever return 429?

No. The gateway has no request-rate limit; a 429 always comes from the destination.

Am I billed for failed requests?

Connections that fail before reaching the target are not billed. A 403 or 429 page from the destination is billed for its size, usually a few kilobytes.

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