HTTP-server-status-codes

Here’s a complete, clear guide to HTTP server status codes — what they mean, how they’re grouped, and real-world examples for each.

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🌐 What Are HTTP Status Codes?

When you visit a website, your browser sends a request to a server. The server replies with a status code — a 3-digit number that tells what happened to your request.

For example:

HTTP/1.1 200 OK

means the request was successful.

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🧩 HTTP Status Code Categories

Category	Range	Meaning
1xx	100–199	Informational responses
2xx	200–299	Success responses
3xx	300–399	Redirection messages
4xx	400–499	Client errors (your side)
5xx	500–599	Server errors (server side)

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🔹 1xx — Informational

These mean the request was received and is being processed.

Code	Message	Example / Explanation
100	Continue	Client can keep sending the rest of the request body
101	Switching Protocols	Used for WebSocket upgrade requests
102	Processing	Server has received the request but not finished processing (used in WebDAV)

🧠 Example:

HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade

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🟢 2xx — Success

These mean your request succeeded.

Code	Message	Example / Explanation
200	OK	Standard success code
201	Created	A new resource was created (e.g., POST /users)
202	Accepted	Request accepted but processing not finished
204	No Content	Success, but no content in response
206	Partial Content	Used for range requests (like video streaming)

🧠 Example:

HTTP/1.1 201 Created
Location: /users/45

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🟡 3xx — Redirection

These tell the browser to go somewhere else.

Code	Message	Example / Explanation
301	Moved Permanently	Resource has a new permanent URL
302	Found	Temporary redirect (commonly used for login pages)
303	See Other	Redirect after POST
304	Not Modified	Browser cache still valid
307	Temporary Redirect	Same as 302 but preserves request method
308	Permanent Redirect	Same as 301 but preserves method

🧠 Example:

HTTP/1.1 301 Moved Permanently
Location: https://newsite.com/

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🔴 4xx — Client Errors

These mean the problem is with the client (browser or request).

Code	Message	Example / Explanation
400	Bad Request	Invalid request syntax
401	Unauthorized	Authentication required
403	Forbidden	You’re not allowed to access
404	Not Found	Page or resource doesn’t exist
405	Method Not Allowed	Wrong HTTP method (e.g., POST on GET endpoint)
408	Request Timeout	Server waited too long for the client
409	Conflict	Request conflicts with server state
410	Gone	Resource deleted permanently
413	Payload Too Large	File upload exceeds limit
429	Too Many Requests	You’re rate-limited

🧠 Example:

HTTP/1.1 404 Not Found

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🔥 5xx — Server Errors

These mean the server failed to fulfill a valid request.

Code	Message	Example / Explanation
500	Internal Server Error	Generic error — something broke on the server
501	Not Implemented	Server doesn’t support the request method
502	Bad Gateway	Server got invalid response from upstream server
503	Service Unavailable	Server overloaded or under maintenance
504	Gateway Timeout	Upstream server didn’t respond in time
505	HTTP Version Not Supported	Request used unsupported HTTP version

🧠 Examples:

HTTP/1.1 500 Internal Server Error

HTTP/1.1 503 Service Unavailable
Retry-After: 120

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🧭 Summary Table

Code	Meaning	Type
100	Continue	Info
200	OK	Success
201	Created	Success
204	No Content	Success
301	Moved Permanently	Redirect
302	Found	Redirect
304	Not Modified	Redirect
400	Bad Request	Client Error
401	Unauthorized	Client Error
403	Forbidden	Client Error
404	Not Found	Client Error
405	Method Not Allowed	Client Error
408	Request Timeout	Client Error
429	Too Many Requests	Client Error
500	Internal Server Error	Server Error
502	Bad Gateway	Server Error
503	Service Unavailable	Server Error
504	Gateway Timeout	Server Error

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🧰 How to Check HTTP Status Codes

🖥️ 1. Using curl

curl -I https://example.com

Output:

HTTP/1.1 200 OK

🕵️ 2. Using Browser Developer Tools

• Open browser → F12 → Network tab → reload site → check "Status" column.

⚡ 3. Using Python

import requests
r = requests.get("https://example.com")
print(r.status_code)

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