HTTP
ベンダー拡張
520 Web Server Returned an Unknown Error
Cloudflare-specific. The origin server returned an unexpected response that Cloudflare could not process.
このコードが表示された場合
When Cloudflare receives an empty, unknown, or malformed response from the origin.
修正方法
Check origin server logs. Ensure responses include proper headers. Verify SSL configuration.
ガイド
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HTTP Redirects: 301 vs 302 vs 307 vs 308
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HTTP Caching: Cache-Control, ETags, and 304 Responses
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Choosing the Right HTTP Status Codes for REST APIs
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gRPC Status Codes: A Practical Guide
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Debugging Timeout Errors: 408 and 504
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401 Unauthorized vs 403 Forbidden: When to Use Each
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Essential HTTP Security Headers
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Complete Guide to HTTP Methods: GET, POST, PUT, PATCH, DELETE
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HTTP/2 vs HTTP/3: What Changed and Why
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How to Implement and Handle Rate Limiting (429)
API Design
API Versioning Strategies: URL, Header, and Query Param
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Designing Consistent API Error Responses
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Debugging 503 Service Unavailable Errors in Production
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TLS/SSL Certificate Troubleshooting Guide
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OAuth 2.0 Flows Explained: Authorization Code, Client Credentials, PKCE
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JSON Web Tokens: Structure, Signing, and Common Pitfalls
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API Keys vs OAuth vs JWT: Choosing the Right Auth Method
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