HEAD and OPTIONS methods in Rest API - Mini Project: Build & Apply

Understanding HEAD and OPTIONS Methods in REST API

📖 Scenario: You are building a simple REST API for a book store. You want to understand how to use the HEAD and OPTIONS HTTP methods to check resource headers and allowed methods without fetching the full data.

🎯 Goal: Learn how to implement and test the HEAD and OPTIONS methods in a REST API to check resource metadata and allowed HTTP methods.

📋 What You'll Learn

Create a simple REST API endpoint for books

Implement the HEAD method to return headers without body

Implement the OPTIONS method to return allowed HTTP methods

Test the API methods and print the results

💡 Why This Matters

🌍 Real World

HEAD and OPTIONS methods help clients check resource info and allowed actions without downloading full data, saving time and bandwidth.

💼 Career

Understanding these HTTP methods is important for backend developers and API designers to build efficient and standards-compliant web services.

1

Set up a basic REST API endpoint for books

Create a list called books with these exact dictionaries: {'id': 1, 'title': '1984'} and {'id': 2, 'title': 'Brave New World'}.

Rest API

# Create a list called books with two dictionaries
# Your code here

Hint

Use a list with two dictionaries exactly as shown.

2

Add a variable for allowed HTTP methods

Create a variable called allowed_methods and set it to the list ['GET', 'POST', 'HEAD', 'OPTIONS'].

Rest API

books = [{'id': 1, 'title': '1984'}, {'id': 2, 'title': 'Brave New World'}]
# Create allowed_methods list
# Your code here

Hint

Use a list with the exact HTTP methods shown.

3

Implement functions to simulate HEAD and OPTIONS methods

Write two functions: head_books() that returns only headers like {'Content-Length': '123'} and options_books() that returns {'Allow': allowed_methods}.

Rest API

books = [{'id': 1, 'title': '1984'}, {'id': 2, 'title': 'Brave New World'}]
allowed_methods = ['GET', 'POST', 'HEAD', 'OPTIONS']

# Define head_books() to return headers only
# Define options_books() to return allowed methods
# Your code here

Hint

Define two functions returning dictionaries as headers and allowed methods.

4

Print the results of HEAD and OPTIONS methods

Print the result of calling head_books() and then print the result of calling options_books().

Rest API

books = [{'id': 1, 'title': '1984'}, {'id': 2, 'title': 'Brave New World'}]
allowed_methods = ['GET', 'POST', 'HEAD', 'OPTIONS']

def head_books():
    # Simulate headers only, no body
    return {'Content-Length': '123'}

def options_books():
    # Return allowed HTTP methods
    return {'Allow': allowed_methods}

# Print the results of head_books() and options_books()
# Your code here

Hint

Use print() to show the returned dictionaries from both functions.

Practice

1. What is the primary purpose of the HEAD method in REST APIs?

easy

A. To create a new resource on the server

B. To delete a resource from the server

C. To update a resource partially

D. To retrieve only the headers of a resource without the body

Solution

1. Step 1: Understand the HEAD method role

   The HEAD method requests headers only, not the full content.

2. Step 2: Compare with other methods

   Unlike GET, it does not return the body, only metadata.

3. Final Answer:

   To retrieve only the headers of a resource without the body -> Option D

4. Quick Check:

   HEAD returns headers only [OK]

Hint: HEAD fetches headers only, no content body [OK]

Common Mistakes:

• Confusing HEAD with GET which returns full content
• Thinking HEAD modifies data on server
• Assuming HEAD returns body content

2. Which of the following is the correct syntax to send an OPTIONS request using curl?

easy

A. curl -X POST https://api.example.com/resource

B. curl -X HEAD https://api.example.com/resource

C. curl -X OPTIONS https://api.example.com/resource

D. curl --get https://api.example.com/resource

Solution

1. Step 1: Identify the method flag in curl

   The -X option specifies the HTTP method to use.

2. Step 2: Match the method to the question

   To send an OPTIONS request, use -X OPTIONS.

3. Final Answer:

   curl -X OPTIONS https://api.example.com/resource -> Option C

4. Quick Check:

   curl -X OPTIONS sends OPTIONS request [OK]

Hint: Use curl -X OPTIONS to send OPTIONS request [OK]

Common Mistakes:

• Using -X HEAD instead of OPTIONS
• Using --get which sends GET request
• Using POST method incorrectly

3. Given the following HTTP response headers from an OPTIONS request:

Allow: GET, POST, OPTIONS, HEAD

What does this header tell the client?

medium

A. The server supports only GET and POST methods

B. The server supports GET, POST, OPTIONS, and HEAD methods on this resource

C. The server denies all methods except OPTIONS

D. The server supports DELETE and PUT methods

Solution

1. Step 1: Read the Allow header

   The Allow header lists HTTP methods the server supports for the resource.

2. Step 2: Interpret the methods listed

   It shows GET, POST, OPTIONS, and HEAD are allowed methods.

3. Final Answer:

   The server supports GET, POST, OPTIONS, and HEAD methods on this resource -> Option B

4. Quick Check:

   Allow header lists supported methods [OK]

Hint: Allow header shows all supported methods [OK]

Common Mistakes:

• Ignoring OPTIONS and HEAD in the list
• Assuming only GET and POST are allowed
• Confusing Allow header with authentication

4. You wrote this code to handle HEAD requests in your REST API server:

if request.method == 'HEAD':
    return get_resource()

But clients receive the full content body. What is the problem?

medium

A. The code returns full content instead of headers only

B. The method name should be lowercase 'head'

C. HEAD requests must be redirected to GET method

D. The server must respond with status 201 for HEAD

Solution

1. Step 1: Analyze the code behavior

   The code calls get_resource() which returns full content including body.

2. Step 2: Understand HEAD response requirements

   HEAD must return headers only, no body content.

3. Final Answer:

   The code returns full content instead of headers only -> Option A

4. Quick Check:

   HEAD returns headers only, not full body [OK]

Hint: HEAD must not return body, only headers [OK]

Common Mistakes:

• Returning full content for HEAD requests
• Using wrong method name case
• Confusing HEAD with GET behavior

5. You want to optimize your REST API by using HEAD and OPTIONS methods. Which approach best improves client efficiency?

hard

A. Use HEAD to check resource existence and OPTIONS to discover allowed methods before sending requests

B. Use OPTIONS to fetch full resource data and HEAD to update resources

C. Use HEAD to delete resources and OPTIONS to create new ones

D. Ignore HEAD and OPTIONS and always use GET and POST

Solution

1. Step 1: Understand HEAD usage

   HEAD checks if a resource exists by fetching headers without body, saving bandwidth.

2. Step 2: Understand OPTIONS usage

   OPTIONS tells clients which HTTP methods are allowed, helping avoid invalid requests.

3. Step 3: Combine for efficiency

   Using both before heavy requests reduces unnecessary data transfer and errors.

4. Final Answer:

   Use HEAD to check resource existence and OPTIONS to discover allowed methods before sending requests -> Option A

5. Quick Check:

   HEAD checks headers, OPTIONS lists methods [OK]

Hint: HEAD checks existence, OPTIONS lists allowed methods [OK]

Common Mistakes:

• Using OPTIONS to fetch full data (wrong)
• Using HEAD to modify resources (wrong)
• Ignoring these methods and wasting bandwidth