It is an NGINX response that originates

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428: Pre-condition required The server signals that specific conditions are required to process the request. 429: Too many requests The server indicates that the speed is limited by the number of requests made at a time. 431: Request header fields too large The headers are too long for the server to process. 451: “Unavailable for legal reasons ” Cannot receive permissions from the browser because the page is censored. It may be due to a lawsuit to prohibit access to the content. 499: Request closed when the client closes the request once processing has started. Server Error Codes 500-599 These codes are signals received when there is an error, the difference between this level and the previous one is that these codes appear when the errors are from the server. 500: “The request could not be completed due to a server error” ( Internal Server Error) It is a generic code that indicates internal error.


It is caused by faulty PHP, third-party plugins, or broken database connections. 501: “Not implemented due to internal error” Occurs if the server does not support the method used by the request and therefore cannot process it. 502: Bad Gateway It may indicate that the server has received a negative response from another server, which may be a proxy. Also that the request took a long time and was cancelled. 503: No service availability This error indicates that the server is Phone Number Data not available to process the request. It can be caused by server overload. 504: Out of stock waiting for response It happens when the server is acting as a gateway and times out because the other server is not responding. 505: HTTP not supported It means that the server cannot support the version of the HTTP protocol used to make the request. 508: “Resource limit reached” It indicates that the server has already reached the resource limit that has been established in your Web Hosting service. 509: “Bandwidth exceeded” It is the server's response when your website uses more bandwidth than your web hosting provider can allow.



511: “Network authentication is required” We can receive it when network authentication is needed before sending a request to the server. It is common when you need to accept policies or terms and conditions when using a public WiFi network. 521: “Server down” Error 521 indicates that there is an error in cloudflare. That is, the server can connect to Cloudflare, but the latter cannot access the origin server. 525: SSL Handshake Failed This is an error message that means the SSL handshake has failed. The failure has occurred between a web domain that uses Cloudflare and the origin server. When we talk about optimizing our website, we must detect flaws. Some of this code originates from the site architecture and can be detected through many tools. A good audit will be your great ally if you want to implement SEO optimization strategies that improve your positioning in the SERPS .