HTTP Reference

Three-in-one HTTP reference: all status codes (1xx–5xx) with reason phrases and use cases; MIME type lookup by extension or Content-Type string; and a comprehensive HTTP headers dictionary with direction, category, description, and usage examples.

Showing 60 of 60 codes
1001xx
Continue
The server has received the request headers, the client should proceed.
1011xx
Switching Protocols
The server agreed to switch protocols as requested.
2002xx
OK
Standard response for successful HTTP requests.
2012xx
Created
The request has been fulfilled and a new resource was created.
2022xx
Accepted
The request has been accepted but processing has not been completed.
2042xx
No Content
Successfully processed; no content returned.
2062xx
Partial Content
Partial resource delivered in response to a range request.
3013xx
Moved Permanently
This and all future requests directed to the given URI.
3023xx
Found
Resource found at a different URI temporarily.
3043xx
Not Modified
Resource has not been modified since specified version.
3073xx
Temporary Redirect
Repeat request with another URI; future requests use original URI.
3083xx
Permanent Redirect
Request and all future requests repeated with another URI.
4004xx
Bad Request
Server cannot process the request due to client error.
4014xx
Unauthorized
Authentication is required and has failed or not been provided.
4034xx
Forbidden
Valid request but server refuses action; user lacks permissions.
4044xx
Not Found
The requested resource could not be found.
4054xx
Method Not Allowed
Request method is not supported for this resource.
4084xx
Request Timeout
The server timed out waiting for the request.
4094xx
Conflict
Request conflicts with the current state of the server.
4104xx
Gone
Resource is no longer available and will not be available again.
4134xx
Payload Too Large
Request is larger than the server is willing to process.
4154xx
Unsupported Media Type
Media type of the request is not supported by the server.
4224xx
Unprocessable Entity
Well-formed request but unable to follow due to semantic errors.
4294xx
Too Many Requests
User has sent too many requests in a given time (rate limiting).
5005xx
Internal Server Error
Generic error when an unexpected condition is encountered on the server.
5015xx
Not Implemented
Server does not recognize the method or lacks ability to fulfill it.
5025xx
Bad Gateway
Server received invalid response from upstream while acting as gateway.
5035xx
Service Unavailable
Server is currently unavailable (overloaded or down for maintenance).
5045xx
Gateway Timeout
Server did not receive a timely response from upstream server.
1000WebSocket
Normal Closure
The connection successfully completed the purpose for which it was created.
1001WebSocket
Going Away
The endpoint is going away (e.g., server shutting down or browser navigating away).
1002WebSocket
Protocol Error
The endpoint is terminating the connection due to a protocol error.
1003WebSocket
Unsupported Data
The connection is being terminated because a data type was received that the endpoint cannot accept.
1005WebSocket
No Status Received
Reserved; no status code was actually present in a close frame.
1006WebSocket
Abnormal Closure
Reserved; used internally when no close frame was sent.
1007WebSocket
Invalid Frame Payload Data
The endpoint received a message whose data was not consistent with the message type.
1008WebSocket
Policy Violation
The endpoint received a message that violates its policy.
1009WebSocket
Message Too Big
The endpoint received a message that is too big to process.
1010WebSocket
Mandatory Extension
The client expected the server to negotiate an extension but did not.
1011WebSocket
Internal Error
The server terminated the connection because it encountered an unexpected condition.
1012WebSocket
Service Restart
The server is restarting.
1013WebSocket
Try Again Later
The server is overloaded; try again later.
1015WebSocket
TLS Handshake Failure
Reserved; TLS handshake failed (e.g. certificate unverifiable).
0gRPC
OK
Not an error; returned on success.
1gRPC
CANCELLED
The operation was cancelled (typically by the caller).
2gRPC
UNKNOWN
Unknown error.
3gRPC
INVALID_ARGUMENT
Client specified an invalid argument.
4gRPC
DEADLINE_EXCEEDED
Deadline expired before operation could complete.
5gRPC
NOT_FOUND
Some requested entity was not found.
6gRPC
ALREADY_EXISTS
The entity attempted to be created already exists.
7gRPC
PERMISSION_DENIED
Caller does not have permission to execute the specified operation.
8gRPC
RESOURCE_EXHAUSTED
Some resource has been exhausted.
9gRPC
FAILED_PRECONDITION
Operation was rejected because the system is not in the required state.
10gRPC
ABORTED
The operation was aborted (concurrency issue or transaction abort).
11gRPC
OUT_OF_RANGE
Operation was attempted past the valid range.
12gRPC
UNIMPLEMENTED
Operation is not implemented or not supported/enabled in this service.
13gRPC
INTERNAL
Internal errors; means some invariant expected by the system has been broken.
14gRPC
UNAVAILABLE
The service is currently unavailable; likely a transient condition.
15gRPC
DATA_LOSS
Unrecoverable data loss or corruption.
16gRPC
UNAUTHENTICATED
The request does not have valid authentication credentials for the operation.

HTTP status codes, WebSocket close codes, gRPC statuses, MIME types, common HTTP headers, a Cache-Control builder, and a content negotiation simulator.

HTTP Reference

Three-in-one HTTP reference: all status codes (1xx–5xx) with reason phrases and use cases; MIME type lookup by extension or Content-Type string; and a comprehensive HTTP headers dictionary with direction, category, description, and usage examples.

Common uses

  • Look up what 422 Unprocessable Entity means
  • Find the MIME type for a .webp file
  • Check what the Vary header does

Also searched as

  • http status codes list with meaning
  • what does 422 unprocessable entity mean
  • mime type for webp
  • extension to mime type lookup
  • http headers list with descriptions
  • cache-control directives explained
  • no-cache vs no-store
  • 502 vs 503 vs 504 difference
  • 429 too many requests meaning
  • accept header content negotiation explained

Frequently asked questions

What does a given HTTP status code mean?

The Status Codes tab lists the standard codes from 1xx to 5xx with reason phrases and descriptions, and you can search by code or name.

How do I find the MIME type for a file extension?

Use the MIME Types tab to look up by extension or by Content-Type string.

What is the difference between no-cache and no-store?

The Cache-Control tab lets you toggle directives such as no-cache, no-store and max-age and builds the header. In short, no-cache requires revalidation before reuse, while no-store forbids storing the response.

Where can I look up what an HTTP header does?

The HTTP Headers tab is a searchable dictionary with request/response direction, category, description and an example, and there is also a Content Negotiation tab for Accept headers.

Is my data uploaded to a server?

No. This tool runs entirely in your browser — your input is processed locally on your device and is never uploaded or stored on a server.