HEAD and OPTIONS methods in Rest API

Introduction

The HEAD and OPTIONS methods help clients learn about a web resource without getting the full content. They make communication faster and clearer.

To check if a web page or file exists without downloading it.

To find out what actions (like GET, POST) a server allows on a resource.

To get metadata like size or last update time of a resource without the full data.

To test if a server is reachable and responding before making a full request.

Syntax

Rest API

HEAD /resource HTTP/1.1
Host: example.com

OPTIONS /resource HTTP/1.1
Host: example.com

The HEAD method requests headers only, no body content.

The OPTIONS method asks the server which HTTP methods it supports for a resource.

Examples

Check if index.html exists and get its headers like content length.

Rest API

HEAD /index.html HTTP/1.1
Host: example.com

Ask the server which methods are allowed on /api/data.

Rest API

OPTIONS /api/data HTTP/1.1
Host: example.com

Sample Program

This Python program sends a HEAD request to check headers of /index.html and an OPTIONS request to see allowed methods. It prints the status codes and headers received.

Rest API

import http.client

conn = http.client.HTTPConnection('example.com')

# Using HEAD method
conn.request('HEAD', '/index.html')
response = conn.getresponse()
print('HEAD status:', response.status)
print('HEAD headers:', response.getheaders())

# Using OPTIONS method
conn.request('OPTIONS', '/index.html')
response = conn.getresponse()
print('OPTIONS status:', response.status)
print('Allow header:', response.getheader('Allow'))

conn.close()

Important Notes

HEAD responses have the same headers as GET but no body content.

OPTIONS responses include an Allow header listing supported methods.

These methods help reduce data usage and improve efficiency.

Summary

HEAD checks resource headers without downloading content.

OPTIONS asks what methods a server supports on a resource.

Both methods help clients communicate efficiently with servers.