400 — Bad Request 错误是一个 HTTP 状态码，当服务器由于请求本身出现问题而无法处理请求时，会弹出该状态码。这是一个客户端问题，这意味着问题来自发送请求的浏览器、工具或代理。
400 错误的常见原因：
- 网址无效： URL 中的拼写错误、特殊字符或格式问题。
- 损坏的 Cookie： 过期或损坏的 cookie 可能会导致问题。
- 超大标题： 超出服务器大小限制的请求标头。
- DNS 问题： 解析网站地址时出现问题。
它如何影响你
400 错误会阻止您访问网页或资源，这可能会令人沮丧并干扰您的工作流程。对于企业而言，反复出现的错误可能会损害用户体验和网站性能。
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Use Cases
Web Scraping With Proxies
A malformed request body sent through a rotating proxy pool will be rejected with 400. Ensuring payload consistency is critical.
Geo-Targeted Requests
If a proxy in one region appends characters incorrectly (e.g., localized symbols), the request may break and return 400.
Browser Automation
Using headless browsers with proxies can generate 400s if session cookies aren’t synced correctly or requests aren’t fully formed.
Best Practices
Rotate Clean Sessions
Don’t rely on stale cookies. With residential or ISP proxies, start fresh sessions to avoid corrupted state leading to 400s.
Validate Before Scaling
Test requests without proxies first. Once you know the request works, scale through proxy pools.
Monitor and Log Errors
Track when 400s occur. If they spike only on certain proxy subnets, it could point to encoding or misconfiguration issues.
Implement Retry Logic Carefully
400 usually means “fix your request,” not “try again.” Avoid blind retries—diagnose and correct the malformed request.
Conclusion
A 400 Bad Request happens when the server can’t understand what was sent. For proxy users, it’s often tied to malformed headers, bad cookies, or misconfigured requests. Clearing sessions, validating requests, and checking proxy settings are the keys to fixing it.
Frequently Asked Question
Does using proxies increase the chance of 400 errors?
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Not directly. A 400 is about malformed requests, not about being blocked. But poor proxy setup (wrong headers, broken cookies) can cause them.
Is a 400 error the same as being blocked?
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No. A block usually returns a 403 Forbidden. A 400 means your request itself was invalid.
Can rotating proxies cause 400 Bad Request?
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Yes, if cookies or headers are reused inconsistently between sessions.
How is 400 different from 422 Unprocessable Entity?
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400 is about malformed syntax. 422 means the syntax is fine, but the server can’t process it due to semantic errors.
