Proxy Error Codes & Troubleshooting: Every Error Your Proxy Throws, Fixed

SOCKS5 Proxy Errors

SOCKS5 Connection Refused

What it looks like:

What it means: The proxy server is reachable, but it's actively rejecting your connection on the specified port.

Common causes:

• Wrong port — SOCKS5 typically uses 1080, not 1081 or other ports
• Username/password incorrect — the proxy authenticates before accepting connections
• Your IP is not allowlisted — some proxy providers whitelist by origin IP
• Proxy account exhausted — no remaining bandwidth or the account is suspended

SOCKS5 Connection Timed Out

What it looks like:

What it means: The proxy server isn't responding within the timeout window. Either it's down, overloaded, or network conditions are preventing the connection.

Common causes:

• Proxy server is overloaded — too many concurrent connections
• Your network is blocking outbound SOCKS5 traffic
• DNS resolution failure — the proxy hostname can't be resolved
• Firewall rules blocking the connection at the network level

How to Test if Your SOCKS5 Proxy Is Working

Use curl to verify your proxy credentials and connectivity:

You can also use the tool at /ip to verify what IP your traffic is exiting from, or check your /headers to confirm X-Forwarded-For and other proxy headers are correctly set.

HTTP Proxy Errors

502 Bad Gateway

What it looks like:

What it means: Your proxy forwarded the request, but the target server returned an invalid or no response. The proxy is working — the target is the problem.

Fixes:

• The target website may be blocking your proxy IP specifically — rotate to a fresh IP
• The target site may be down or rate-limiting — try again with a delay
• DNS issues on the proxy server side — try a different proxy endpoint
• Increase your client timeout — the proxy may be timing out waiting for the target

408 Request Timeout

What it looks like:

What it means: The target server closed the connection because it took too long to receive the complete request. This is usually a network speed issue between your proxy and the target.

Fixes:

• Reduce the payload size of your request
• Switch to a proxy node with lower latency to the target
• Use HTTP/1.1 keep-alive to reuse connections
• Increase your HTTP client's timeout setting

ERR_TUNNEL_CONNECTION_FAILED

What it looks like:

What it means: Chrome can't establish a CONNECT tunnel through the proxy to the target HTTPS site. The proxy itself is reachable, but it can't complete the connection to the destination.

Fixes:

• The proxy may not support HTTPS tunneling — verify it supports CONNECT method
• The target site may be blocking the proxy's IP — try a different proxy
• Corporate or ISP firewall blocking HTTPS over proxy
• Proxy authentication is failing silently — re-check username/password

Proxy Authentication Required (HTTP 407)

What it looks like:

What it means: The proxy server received your request but requires authentication before forwarding it. Your credentials are either missing or incorrect.

Fixes:

• Check your Proxy-Authorization header is correctly formatted
• Verify your proxy username and password — check for special characters that need URL encoding
• For SOCKS5 proxies, authentication is handled at the protocol level — ensure your client library sends auth on connect

Common Non-Error Proxy Problems

"My proxy works but I keep getting CAPTCHAs"

Problem: The proxy connects successfully — no errors — but every site shows a CAPTCHA or challenge page.

Fix: Your proxy IP is flagged as suspicious. Datacenter IPs get this constantly. Switch to a residential or mobile proxy IP — they have real consumer ISP reputations and pass anti-bot checks. If you're already on residential, rotate to a fresh IP — the current one may have been burned by a previous user.

"My proxy speed is extremely slow"

Problem: Proxy connects but transfers data at dial-up speeds.

Fix: Residential proxies route through home internet connections, which are inherently slower than datacenter links. To improve speed: (1) select a proxy geographically closer to your target server, (2) use mobile (4G/5G) proxies for higher throughput, (3) ensure your proxy provider supports connection pooling to avoid TCP handshake overhead on every request, (4) check if you're hitting bandwidth throttling on the proxy node.

"Requests succeed sometimes but fail randomly"

Problem: Intermittent proxy failures — works 70% of the time, fails 30%.

Fix: This is usually a pool quality issue. Your proxy is rotating through IPs, and some are burned while others are clean. Use a provider with self-healing routing (like ProxyBase's dual-path failover) that automatically detects failed paths and re-routes. Alternatively, implement retry logic with automatic IP rotation on failure in your client code.

Quick Diagnostic Checklist

When your proxy isn't working, run through these checks in order:

1. Credentials — are username and password correct? Are special characters URL-encoded?
2. Host and port — is the proxy server hostname resolving? Is the port correct (SOCKS5: 1080, HTTP: typically 8080 or 3128)?
3. Firewall — can you reach the proxy server at all? Try `telnet proxy.example.com 1080`
4. Bandwidth — have you exhausted your proxy account? Check your remaining data
5. IP reputation — is the proxy IP blocked by the target? Try a different IP or rotation
6. Protocol — are you using the right protocol? SOCKS5 and HTTP proxies are different
7. DNS — is DNS resolution happening at the proxy or locally? SOCKS5h resolves at the proxy, SOCKS5 resolves locally
8. Timeout — is your client timeout too short? Try 30+ seconds for residential proxies