Proxy errors 403, 407 and 429 explained
Three status codes account for most proxy trouble. They come from different parties, which tells you where to look.
407: the proxy refused you
Proxy Authentication Required. The proxy, not the target, is saying no. Check the username and password, or confirm your sending address is on the allowlist.
403: the target refused the address
Forbidden. The site is serving you but will not give you this page. Typical causes are a server address range the site blocks, a poor reputation for the address, or missing browser headers. Try an ISP address instead of datacenter, or check that your client looks like a normal browser.
429: too many requests
You exceeded a rate limit. Slow down, add a delay with some randomness, and spread requests over more addresses. A Retry-After header, when present, says how long to wait.
A short triage
Work through these in order.
- Is it 407? Fix authentication first.
- Does the same request work without the proxy? If so, the address is the issue.
- Does it work from a different address? If so, that address is flagged.
- Does it fail only at speed? Reduce concurrency.
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Put it into practice
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