Question 1

What are HTTP status codes?

Accepted Answer

HTTP status codes are three-digit numbers returned by a server in response to a client's request. They are grouped into five classes: 1xx (informational), 2xx (success), 3xx (redirection), 4xx (client errors), and 5xx (server errors). Every HTTP response includes a status code that tells the client whether the request was successful or what went wrong.

Question 2

What is the difference between 401 and 403?

Accepted Answer

401 Unauthorized means the client is not authenticated — it needs to provide valid credentials (e.g., log in). 403 Forbidden means the client is authenticated but does not have permission to access the resource. In short: 401 = 'who are you?', 403 = 'I know who you are, but you cannot access this'.

Question 3

When should I use 301 vs 302 redirects?

Accepted Answer

Use 301 (Moved Permanently) when a URL has changed forever and you want search engines to update their index and transfer SEO equity to the new URL. Use 302 (Found / Temporary Redirect) when the redirect is temporary and you want to keep the original URL in search engine indexes. For modern applications, 308 (Permanent Redirect) and 307 (Temporary Redirect) are preferred as they strictly preserve the HTTP method.

Question 4

What causes a 500 Internal Server Error?

Accepted Answer

A 500 Internal Server Error is a generic catch-all for unexpected server-side failures. Common causes include unhandled exceptions in application code, database connection failures, misconfigured server settings, out-of-memory errors, or bugs in server-side logic. Check your server error logs for the specific stack trace and root cause.

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HTTP Status Codes Reference