HTTP Status Codes

An HTTP status code is a three-digit number sent by a web server in response to a client's request. The first digit indicates the category: 1xx (informational), 2xx (success), 3xx (redirection), 4xx (client error), or 5xx (server error). Status codes tell the browser or API client what happened with the request.

HTTP 404 Not Found means the server cannot find the requested resource at the specified URL. Common causes include typos in the URL, deleted pages, broken links, or incorrect API endpoints. The resource may exist at a different URL or may have been removed entirely.

HTTP 500 Internal Server Error is a generic server-side error indicating something went wrong but the server cannot be more specific. Common causes include application bugs, database connection failures, unhandled exceptions, or misconfigured server settings. Check server logs for the specific cause.

HTTP 401 Unauthorized means authentication is missing or invalid—the server does not know who you are. HTTP 403 Forbidden means the server knows who you are but you do not have permission to access the resource. Fix 401 by providing valid credentials; fix 403 by requesting appropriate access permissions.

HTTP 301 Moved Permanently tells browsers and search engines the resource has permanently moved to a new URL; future requests should use the new URL. HTTP 302 Found indicates a temporary redirect where the original URL is still valid. Use 301 for permanent URL changes and 302 for temporary redirects.

HTTP 502 Bad Gateway means a server acting as a gateway or proxy received an invalid response from an upstream server. Common causes include crashed backend services, network issues between servers, or misconfigured reverse proxies like Nginx or load balancers.

HTTP 503 Service Unavailable means the server is temporarily unable to handle the request, usually due to maintenance or being overloaded. Unlike 500, this implies a temporary condition. The server should include a Retry-After header indicating when to try again.

HTTP 429 Too Many Requests means you have exceeded the server's rate limit. Wait before sending more requests. Check the Retry-After response header for the recommended delay. APIs use this status code to prevent abuse and ensure fair usage among all clients.

HTTP 200 OK means the request was successful. The server found the requested resource and returned it. This is the standard response for every normal page load. For POST requests, it indicates the action was successfully completed.

HTTP 304 Not Modified means the resource has not changed since the browser last requested it. Instead of sending the full response again, the server tells the browser to use its cached copy. This saves bandwidth and speeds up page loads.

An HTTP status code is a three-digit number sent by a web server in response to a client's request. The first digit indicates the category: 1xx (informational), 2xx (success), 3xx (redirection), 4xx (client error), or 5xx (server error). Status codes tell the browser or API client what happened with the request.

HTTP 404 Not Found means the server cannot find the requested resource at the specified URL. Common causes include typos in the URL, deleted pages, broken links, or incorrect API endpoints. The resource may exist at a different URL or may have been removed entirely.

HTTP 500 Internal Server Error is a generic server-side error indicating something went wrong but the server cannot be more specific. Common causes include application bugs, database connection failures, unhandled exceptions, or misconfigured server settings. Check server logs for the specific cause.

HTTP 401 Unauthorized means authentication is missing or invalid—the server does not know who you are. HTTP 403 Forbidden means the server knows who you are but you do not have permission to access the resource. Fix 401 by providing valid credentials; fix 403 by requesting appropriate access permissions.

HTTP 301 Moved Permanently tells browsers and search engines the resource has permanently moved to a new URL; future requests should use the new URL. HTTP 302 Found indicates a temporary redirect where the original URL is still valid. Use 301 for permanent URL changes and 302 for temporary redirects.

HTTP 502 Bad Gateway means a server acting as a gateway or proxy received an invalid response from an upstream server. Common causes include crashed backend services, network issues between servers, or misconfigured reverse proxies like Nginx or load balancers.

HTTP 503 Service Unavailable means the server is temporarily unable to handle the request, usually due to maintenance or being overloaded. Unlike 500, this implies a temporary condition. The server should include a Retry-After header indicating when to try again.

HTTP 429 Too Many Requests means you have exceeded the server's rate limit. Wait before sending more requests. Check the Retry-After response header for the recommended delay. APIs use this status code to prevent abuse and ensure fair usage among all clients.

HTTP 200 OK means the request was successful. The server found the requested resource and returned it. This is the standard response for every normal page load. For POST requests, it indicates the action was successfully completed.

HTTP 304 Not Modified means the resource has not changed since the browser last requested it. Instead of sending the full response again, the server tells the browser to use its cached copy. This saves bandwidth and speeds up page loads.