HTML ReferencesLesson #85
HTTP Messages
Every time a browser asks a server for something, the server sends back a short code that says how it went. This code is called an HTTP status code.
HTTP Response Status Codes
Every time a browser asks a server for something, the server sends back a short code that says how it went. This code is called an HTTP status code.
HTTP status codes tell developers if a request worked, was sent somewhere else (redirected), or failed.
The server sends a status code for every request, even when you do not see it. The most common code is 200 OK, which means everything worked.
Below is a list of HTTP status codes that can be returned:
Informational Codes (100-199)
| Code | Description |
|---|---|
| 100 Continue | The server has received the request headers, and the client should proceed to send the request body |
| 101 Switching Protocols | The requester has asked the server to switch protocol |
| 103 Early Hints | Used with the Link header to allow the browser to start preloading resources while the server prepares a response |
Successful Codes (200-299)
| Code | Description |
|---|---|
| 200 OK | The request is OK (this is the standard response for successful HTTP requests) |
| 201 Created | The request has been fulfilled, and a new resource is created |
| 202 Accepted | The request has been accepted for processing, but the processing has not been completed |
| 203 Non-Authoritative Information | The request has been successfully processed, but is returning information that may be from another source |
| 204 No Content | The request has been successfully processed, but is not returning any content |
| 205 Reset Content | The request has been successfully processed, but is not returning any content, and requires that the requester reset the document view |
| 206 Partial Content | The server is delivering only part of the resource due to a range header sent by the client |
Redirection Codes (300-399)
| Code | Description |
|---|---|
| 300 Multiple Choices | A link list. The user can select a link and go to that location. Maximum five addresses |
| 301 Moved Permanently | The requested page has moved to a new URL |
| 302 Found | The requested page has moved temporarily to a new URL |
| 303 See Other | The requested page can be found under a different URL |
| 304 Not Modified | Indicates the requested page has not been modified since last requested |
| 307 Temporary Redirect | The requested page has moved temporarily to a new URL |
| 308 Permanent Redirect | The requested page has moved permanently to a new URL |
Client Error Codes (400-499)
| Code | Description |
|---|---|
| 400 Bad Request | The request cannot be fulfilled due to bad syntax |
| 401 Unauthorized | The request was a legal request, but the server is refusing to respond to it. For use when authentication is possible but has failed or not yet been provided |
| 402 Payment Required | Reserved for future use |
| 403 Forbidden | The request was a legal request, but the server is refusing to respond to it |
| 404 Not Found | The requested page could not be found but may be available again in the future |
| 405 Method Not Allowed | A request was made of a page using a request method not supported by that page |
| 406 Not Acceptable | The server can only generate a response that is not accepted by the client |
| 407 Proxy Authentication Required | The client must first authenticate itself with the proxy |
| 408 Request Timeout | The server timed out waiting for the request |
| 409 Conflict | The request could not be completed because of a conflict in the request |
| 410 Gone | The requested page is no longer available |
| 411 Length Required | The "Content-Length" is not defined. The server will not accept the request without it |
| 412 Precondition Failed | The precondition given in the request evaluated to false by the server |
| 413 Content Too Large | The server will not accept the request, because the request body is too large |
| 414 URI Too Long | The server will not accept the request, because the URI is too long. Occurs when you convert a POST request to a GET request with a long query information |
| 415 Unsupported Media Type | The server will not accept the request, because the media type is not supported |
| 416 Range Not Satisfiable | The client has asked for a portion of the file, but the server cannot supply that portion |
| 417 Expectation Failed | The server cannot meet the requirements of the Expect request-header field |
| 429 Too Many Requests | The client must has sent too many requests in a given time period |
Server Error Codes (500-599)
| Code | Description |
|---|---|
| 500 Internal Server Error | A generic error message, given when no more specific message is suitable |
| 501 Not Implemented | The server either does not recognize the request method, or it lacks the ability to fulfill the request |
| 502 Bad Gateway | The server was acting as a gateway or proxy and received an invalid response from the upstream server |
| 503 Service Unavailable | The server is currently unavailable (overloaded or down) |
| 504 Gateway Timeout | The server was acting as a gateway or proxy and did not receive a timely response from the upstream server |
| 505 HTTP Version Not Supported | The server does not support the HTTP protocol version used in the request |
| 511 Network Authentication Required | The client needs to authenticate to gain network access |
Interactive Code Examples
HTTP Messages Example
htmlLive code example for HTTP Messages. Click Try it Yourself to test.
<!DOCTYPE html>
<html>
<head>
<style>
body {
font-family: system-ui, -apple-system, sans-serif;
padding: 24px;
background: #f8fafc;
color: #0f172a;
}
.demo-card {
background: #ffffff;
padding: 24px;
border-radius: 16px;
border: 1px solid #e0e7ff;
box-shadow: 0 10px 25px -5px rgba(79, 70, 229, 0.08);
max-width: 540px;
}
h2 { color: #4f46e5; margin-top: 0; font-size: 22px; }
p { color: #64748b; line-height: 1.6; }
.btn {
display: inline-flex;
align-items: center;
gap: 8px;
background: #4f46e5;
color: #ffffff;
border: none;
padding: 10px 20px;
border-radius: 9999px;
font-weight: 700;
font-size: 13px;
cursor: pointer;
box-shadow: 0 4px 12px rgba(79, 70, 229, 0.25);
}
.btn:hover { background: #4338ca; }
</style>
</head>
<body>
<div class="demo-card">
<h2>HTTP Messages</h2>
<p>This is a live runnable interactive demonstration for <strong>HTTP Messages</strong>.</p>
<button class="btn" onclick="alert('Testing HTTP Messages!')">
<span>Interactive Action</span> →
</button>
</div>
</body>
</html>