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- Reference for Abnormal Status Codes
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Reference for Abnormal Status Codes

EdgeOne responds with the following types of exception status codes:
Standard Status Codes
You can refer to the HTTP Status Code Standard to see the specific meanings of these status codes. These codes are typically responded to in the following situations:
After the request is sent back to the origin, the status code information is responded by the origin server, and the node will pass transmit status code from the origin server to the client.
Direct responses from EdgeOne nodes, for example, Token authentication fails, responding with a 403 status code. Possible status codes that may be directly responded by EdgeOne nodes include the following status ones:
Status Code
Description
400
The client's request is deemed invalid because the requested method is not within the allowed range set by EdgeOne. For details, see HTTP Restrictions.
403
Fail to pass the link protection verification, such as the Token authentication in the rule engine.
416
Range exception, for example, rangeStart < 0,< 0, rangeStart > rangeStart > rangeEnd, or rangeStart > FileSize.
418
For each domain name connected to EdgeOne, the system automatically allocates service nodes for the domain. Each corresponding node receives the domain's configuration file, which includes settings such as the origin server, cache, headers, etc. When a request is sent to a node, it reads the domain's configuration file. If the file is not found, the node responds with a 418 status code. For example, if a client sends a request to http://example.com/test.jpg, the node reads the configuration file for the domain example.com. If, due to reasons such as the service node binding to a non-example.com domain name, CNAME configuration errors, or issues with the scheduling system, the configuration file is not found, the client will receive a 418 response.
423
Request loopback is triggered, that is, the Loops value in the CDN-Loop header is greater than or equal to 16. For details, see CDN-Loop.
EdgeOne Custom Status Codes
EdgeOne defines special status codes with unique meanings. Status codes within the range of 499 and 520-599 are reserved by EdgeOne for custom non-standard responses. It is recommended to avoid using status codes within this range in your business to prevent confusion with EdgeOne's status codes.
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Below are the custom EdgeOne status codes along with their meanings, facilitating self-troubleshooting when encountering abnormal business access.
Status Code
Meaning Explanation
499
The client's request reaches the node, and if the client disconnects before receiving a response from the node, such as closing the request page, the log and monitoring will record it as status code 499.
520/550
After the node successfully establishes a connection with the origin server and sends a request, if the origin server directly sends a RST packet, the node responds to the client with a 520 status code.
521/551
When the node requests the origin server, during the TCP connection establishment phase, if the origin server directly sends a RST packet, the node responds to the client with a 521 status code.
522/552
When the node requests the origin server, during the TCP connection establishment phase, if the origin server does not respond, causing the node to time out, the node responds to the client with a 522 status code.
523/553
If the domain is configured with a domain name as the origin server, when the node goes to the origin, it needs to resolve the domain to obtain the origin server's IP. If the resolution fails, the node cannot go to the origin, and it responds to the client with a 523 status code.
524/554
After successfully establishing a connection with the origin server, if the node initiates a request to the origin server and there is no response from the origin server, causing a timeout at the node, the node responds to the client with a 524 status code.
525/555
If the origin protocol is HTTPS, the node needs to perform an SSL handshake with the origin server when going back to the source. If the handshake fails, the node responds to the client with a 525 status code.
566
When a request is intercepted by Web Protection - Managed Rules, the default response is a 566 status code along with the default interception page. If the user has configured a custom interception status code, the configured status code will be used.
567
When a request is intercepted by Web Protection - Custom Rules, Web Protection - Rate Limiting or Bot Management rules, the default response is a 567 status code along with the default interception page. If the user has configured a custom interception status code, the configured status code will be used.
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Standard Status Codes
EdgeOne Custom Status Codes

Status Code	Description
400	The client's request is deemed invalid because the requested method is not within the allowed range set by EdgeOne. For details, see HTTP Restrictions.
403	Fail to pass the link protection verification, such as the Token authentication in the rule engine.
416	Range exception, for example, rangeStart < 0,< 0, rangeStart > rangeStart > rangeEnd, or rangeStart > FileSize.
418	For each domain name connected to EdgeOne, the system automatically allocates service nodes for the domain. Each corresponding node receives the domain's configuration file, which includes settings such as the origin server, cache, headers, etc. When a request is sent to a node, it reads the domain's configuration file. If the file is not found, the node responds with a 418 status code. For example, if a client sends a request to `http://example.com/test.jpg`, the node reads the configuration file for the domain `example.com`. If, due to reasons such as the service node binding to a `non-example.com` domain name, CNAME configuration errors, or issues with the scheduling system, the configuration file is not found, the client will receive a 418 response.
423	Request loopback is triggered, that is, the Loops value in the CDN-Loop header is greater than or equal to 16. For details, see CDN-Loop.

Status Code	Meaning Explanation
499	The client's request reaches the node, and if the client disconnects before receiving a response from the node, such as closing the request page, the log and monitoring will record it as status code 499.
520/550	After the node successfully establishes a connection with the origin server and sends a request, if the origin server directly sends a RST packet, the node responds to the client with a 520 status code.
521/551	When the node requests the origin server, during the TCP connection establishment phase, if the origin server directly sends a RST packet, the node responds to the client with a 521 status code.
522/552	When the node requests the origin server, during the TCP connection establishment phase, if the origin server does not respond, causing the node to time out, the node responds to the client with a 522 status code.
523/553	If the domain is configured with a domain name as the origin server, when the node goes to the origin, it needs to resolve the domain to obtain the origin server's IP. If the resolution fails, the node cannot go to the origin, and it responds to the client with a 523 status code.
524/554	After successfully establishing a connection with the origin server, if the node initiates a request to the origin server and there is no response from the origin server, causing a timeout at the node, the node responds to the client with a 524 status code.
525/555	If the origin protocol is HTTPS, the node needs to perform an SSL handshake with the origin server when going back to the source. If the handshake fails, the node responds to the client with a 525 status code.
566	When a request is intercepted by Web Protection - Managed Rules, the default response is a 566 status code along with the default interception page. If the user has configured a custom interception status code, the configured status code will be used.
567	When a request is intercepted by Web Protection - Custom Rules, Web Protection - Rate Limiting or Bot Management rules, the default response is a 567 status code along with the default interception page. If the user has configured a custom interception status code, the configured status code will be used.