What does a 404 Not Found error mean?

The 404 error indicates the server could not find the requested resource. It is one of the most common HTTP errors, typically occurring when a URL has changed, the page was deleted, or a link is broken. To fix it, verify the URL, check incoming links, and set up 301 redirects if content was moved.

What is a 500 Internal Server Error?

The 500 error is a generic response indicating the server encountered an unexpected condition that prevents it from fulfilling the request. It can be caused by PHP/Python/Node.js code errors, incorrect server configurations (nginx, Apache), dependency issues, or insufficient memory. Check server logs to identify the root cause.

What causes a 502 Bad Gateway error?

A 502 error occurs when a server acting as a gateway or proxy receives an invalid response from the upstream server. It is frequently caused by crashed Docker containers, application timeouts, network issues between the reverse proxy and backend, or PHP-FPM/Unicorn/Puma services that stopped responding.

What is the difference between 301 and 302 redirects?

301 (Moved Permanently) indicates the resource has been permanently moved. Search engines update their indexes to the new URL and transfer PageRank. 302 (Found) is a temporary redirect — search engines keep the original URL in their results. Use 301 for permanent changes and 302 for maintenance or A/B testing.

What does a 403 Forbidden error mean?

A 403 error indicates the server understood the request but refuses to authorize it. Common causes include: incorrect file permissions (chmod), misconfigured IAM policies on AWS/GCP/Azure, WAF (Web Application Firewall) rules blocking the request, or IP restrictions in .htaccess or nginx.

HTTP Codes | Tecniwao

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Common errors in production

502 Bad Gateway: Frequently caused by crashed containers, application timeouts, or network issues between reverse proxy and backend.
504 Gateway Timeout: Generally indicates slow database queries, unresponsive external services, or insufficient capacity.
503 Service Unavailable: Usually during deploys, maintenance, or when auto-scaling cannot handle the load.
403 Forbidden: Can range from incorrectly configured file permissions to incorrect IAM policies in the cloud.

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Common errors in production

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