ERROR CODE

Client-Side Errors (5xx)

400 — Bad Request The server cannot understand or process your request because something is wrong with it (wrong format, missing data, invalid input).

Example: You fill out a form on a website and enter an invalid email format (like “abc@def” without .com), so the server rejects it with “Bad Request”.

401 — Unauthorized You need to log in or provide valid authentication (like a password, token, or API key), but you didn’t or it’s wrong/expired.

Example: Trying to open your Gmail without logging in, or your login session/token has expired.

403 — Forbidden The server knows who you are (you’re authenticated), but you don’t have permission to access that specific resource.

Example: You click on a private GitHub repository link, but you don’t have access rights — you get “Forbidden”.

404 — Not Found The server can’t find the requested page or resource — it doesn’t exist (or was deleted/moved).

Example: You type “www.example.com/about-us" but the real page is “www.example.com/about" → server shows “404 Not Found”.

429 — Too Many Requests You (or your app) sent too many requests in a short time, so the server is rate-limiting you to prevent overload or abuse.

Example: Sending hundreds of API calls per minute from a script, or refreshing a page too aggressively.

Server-Side Errors (5xx)

These mean something went wrong on the server’s side (not your fault).

500 — Internal Server Error A general server error — something unexpected crashed or failed inside the server (code bug, database issue, overload, etc.).

Example: On Daraz.pk, you click “Buy Now” or “Place Order”, but the payment system crashes or the database gets overloaded → server shows “500 Internal Server Error”.

501 — Not Implemented The server doesn’t support the method or feature you’re trying to use (it’s not built/implemented yet).

Example: An old website only supports GET and POST requests, but your browser or tool tries to use PATCH (or another method) → server replies “Not Implemented”.

502 — Bad Gateway The server (acting as a gateway/proxy) received an invalid or bad response from another server it’s talking to (like a backend or upstream service).

Example: Streaming Netflix — the main Netflix server forwards your request to a CDN (content delivery network), but the CDN is down or sends back garbage → you get “Bad Gateway”.

503 — Service Unavailable The server is temporarily unable to handle the request (usually because it’s overloaded, under maintenance, or too many users).

Example: During Daraz’s 11.11 mega sale, millions of people are adding items to cart at the same time → server gets overloaded and shows “503 Service Unavailable”.

504 — Gateway Timeout The server (acting as a gateway) waited too long for a response from another server (upstream service timed out).

Example: On Booking.com, you search for flights — the site sends your request to the airline’s server, but the airline’s system is slow or down → you get “504 Gateway Timeout”.